Small ui improvements

* make file tree row 2px smaller for more compact view
* make sub navigation  background a bit darker for better contrast with main navigation

cc @hazelyang @alfredo1 

See merge request !5315

Update documentation for build artifact dependencies

## What does this MR do?

Update documentation for build artifact dependencies

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

#19892 

## What are the relevant issue numbers?

#19892 

## Screenshots (if relevant)


See merge request !5332

Update MAINTENANCE.md with our latest policy

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19958

See merge request !5339

[ci skip]

Fix of 'Commits being passed to custom hooks are already reachable when using the UI'

This is back-port of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/563

## What does this MR do?
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19771
This MR changes the way how we create commit, we create it directly in the branch and we don't use temporary ref anymore. This also works similar to how `git-receive-pack` works so it's a natural way to create commit.


## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ce/issues/19771

See merge request !5337

Upgrade gemojione to 3.0.0

Upgrades gemojione to 3.0.0, see the Changelog: https://github.com/jonathanwiesel/gemojione/blob/b98aa8b07eef815d4d3f52ff3c8714b28932b0de/CHANGELOG.md#v300-2016-07-12

[Here are all the new 2016 emoji](http://emojione.com/releases/2.2.4/) 🎉

This update has new emoji and more sensical categories.

See merge request !5237

Fixed the alignment in the MR widget

## What does this MR do?

Fixes the alignment of the browse button in the MR widget

## Screenshots (if relevant)

![Screen_Shot_2016-07-17_at_17.47.54](/uploads/41dcb0fad38fdd4dbccfda5ffaeaec6e/Screen_Shot_2016-07-17_at_17.47.54.png)

See merge request !5307

Blurs the clicked link in dropdown menus

## What does this MR do?

This fixes an issue where the dropdown menu would stay visible even when clicked out of it

See merge request !5322

Improve cron_jobs loading error messages

## What does this MR do?

Improves the error message from "Sidekiq Cron Jobs" plugin, when trying to load a incorrect definition from gitlab config files.

This is the output before the fix:

```
2016-06-08T16:43:19.277Z 2890 TID-gso49ojro INFO: Booting Sidekiq 4.1.2 with redis options {:url=>"unix:/var/run/redis/redis.sock", :namespace=>"resque:gitlab"}
undefined method `delete' for nil:NilClass
/home/git/gitlab/config/initializers/sidekiq.rb:16:in `block (2 levels) in <top (required)>'
/home/git/gitlab/config/initializers/sidekiq.rb:16:in `each'
/home/git/gitlab/config/initializers/sidekiq.rb:16:in `block in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/sidekiq-4.1.2/lib/sidekiq.rb:70:in `configure_server'
```

This is the output after the fix:

```
2016-07-18T10:53:22.414Z 66332 TID-oxal1bmik INFO: Booting Sidekiq 4.1.4 with redis options {:url=>"redis://localhost:6378", :namespace=>"resque:gitlab"}
Invalid cron_jobs config key: 'registry'. Check your gitlab config file.
/home/git/gitlab/config/initializers/sidekiq.rb:21:in `block (2 levels) in <top (required)>'
/home/git/gitlab/config/initializers/sidekiq.rb:17:in `each'
/home/git/gitlab/config/initializers/sidekiq.rb:17:in `block in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/ruby-2.1.8/gems/sidekiq-4.1.4/lib/sidekiq.rb:70:in `configure_server'
```

Fixes #18378

## Are there points in the code the reviewer needs to double check?

No

## Why was this MR needed?

Original error doesn't give any hint on where the problem can be, so the user can't easily troubleshoot unless he knows implementation details.

## What are the relevant issue numbers?

#18378

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5318

Allow build email service to be tested

Fixes #13343 

See merge request !5223

Content Security Policy

Ref: #18231 

This uses twitter's [secure_headers gem](https://github.com/twitter/secureheaders).

See merge request !4770

Collapsed diffs lines/size don't accumulate to overflow diffs.

## What does this MR do?

Reduce the number of lines that we highlight on big diffs to try to reduce the degradation introduced by  !4990 as you can see on the issue description #19820 .

We collapse any files after the diff is over the number of safe files (100), or over the safe lines (500) or over the safe number of bytes (5KB x 100 files).

We still need to bump the gitlab_git and point this branch to the new gitlab_git version.

## What are the relevant issue numbers?

Closes #19820 
Closes #19885

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- ~~[ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~[ ] API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)


See merge request !5306

Render only commit title

## What does this MR do?
Render only commit title in builds



## Why was this MR needed?
Better readability

## What are the relevant issue numbers?
Closes #19420 

## Screenshots (if relevant)
![after](/uploads/fcdd59d74a0f91f6ac847f7f02d5f07f/after.png)![before](/uploads/71ca6dabf31452a1a8dfb15ecb8860c5/before.png)
## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added


- Tests

- [x] All builds are passing
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

cc: @kradydal @yorickpeterse @grzesiek @tmaczukin @dzaporozhets [@tomash](https://github.com/tomash) [@chastell](https://github.com/chastell)

this is connected to closed MR [!5109](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5109)

See merge request !5131

Gravatar, Google Analytics, Piwik, Recaptcha, etc.

Improve markdown

Based on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4975 (thanks @sheerun) with small changes on top

cc @iamphill @tauriedavis 

See merge request !5314

This adds the 2016 emoji as well as support for using SVG images instead of PNGs.

It also fixes a number of incorrectly categorized emoji and other minor issues.

Upgrade Rake task for Gemojione 3.0.0 and generate sprites.

Upgrade aliases.json by pulling down index.json from the gemojione repository and running the generate_aliases.rb file.

Changelog: https://github.com/jonathanwiesel/gemojione/blob/master/CHANGELOG.md#v301-2016-07-16

For the specific emoji added to the Unicode standard, see: http://emojione.com/releases/2.2.4/

Huge kudos to Jonathan Wiesel (@jonathanwiesel) for his work on the gemojione gem!

Revert "Revert "Merge branch '18193-developers-can-merge' into 'master'""

## What does this MR do?

Reverts the revert of !4892 which lacked an EE MR at the time. This has been done in gitlab-org/gitlab-ee!564.

## What are the relevant issue numbers?

Closes #19872.

See merge request !5310

Fix activity heatmap to show proper day name.

## What does this MR do?
This MR fixes issue #19909.

## Are there points in the code the reviewer needs to double check?
Not necessarily, it's pretty straightforward, buuuut

There was some discussion about whether GL wanted the activity heatmap to start on Monday or Sunday, this fix makes it start on Sunday, if GL is wanting it to start on Monday then some more substantial changes need to be made on the `calendar.js.coffee` script.

## Why was this MR needed?
The amount of day names that were off from their dates was too damn high! :P 

## What are the relevant issue numbers?
Directly #19909 

Also some related discussion (feature discussion):
#19282, #5988

## Screenshots (if relevant)
**Currently on GL.com**
![Screen_Shot_2016-07-16_at_10.56.02_PM](/uploads/b45cfc56c29a8865a2bdc1f798409706/Screen_Shot_2016-07-16_at_10.56.02_PM.png)

**After MR**
![Screen_Shot_2016-07-16_at_10.56.30_PM](/uploads/d8655bb259ced443a2c572ff03dcb8bb/Screen_Shot_2016-07-16_at_10.56.30_PM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5303

This fixes an issue where the dropdown menu would stay visible even when clicked out of it

Don't blow up in tree view on empty repo

## What does this MR do?

Stop the empty repo page blowing up with a 500 error when a user's default view is tree view.

## Are there points in the code the reviewer needs to double check?

Don't think so.

## Why was this MR needed?

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4997 made sure that the `tree` filter was only called if the user's default project view is tree, but left out the empty repo check. When users visit an empty repo with the tree view as default, they now get a 500.

## What are the relevant issue numbers?

Closes #19928.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- ~~[CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added~~ (bug introduced in same release)
- ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~API support added~~
- Tests
  - ~~Added for this feature/bug~~
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)


See merge request !5317

Don't parse Rinku returned value to DocFragment when didn't change original html string.

See merge request !5311

- This was introduced (at some point) while rebasing `master` against
  the "developers can merge" feature branch.

- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5310#note_13139705