Remove Rack Attack monkey patches and bump to version 4.3.0

I finally got these monkey patches into Rack Attack v4.3.0, so GitLab no longer needs them. Hooray!

See: https://github.com/kickstarter/rack-attack/pull/128

See merge request !693

Added documentation styleguide

Hi. I added a documentation styleguide and linked it to https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides

See merge request !709

Document expanded autolinking in doc/markdown/markdown.md

See merge request !706

Disable "New Issue" and "New Merge Request" buttons when features are disabled in project settings

Closes #1676

See merge request !691

Closes #1676

Remove redundant CHANGELOG entry

This was moved into v7.10.4, but I forgot to delete it from the v7.11 list.

See merge request !692

Add support for Webhook note events

This MR adds support for note events (comments) for WebHooks.

Perhaps the only potential source of confusion is that the settings indicates "Note Events" instead of "Comments". What do you think?

Screenshot after:

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/299b141d82f7b14943a74258d5c57ca6/image.png)

Closes https://github.com/gitlabhq/gitlabhq/issues/6745

See merge request !673

Use the user list from the target project in a merge request

### What does this MR do?

This MR derives the assignable users from the target project.

### Why was this MR needed?

In a merge request, the assignable users uses the list from the forked project, not the target project where the merge request will be going. For example, if I fork a project from the gitlab-org namespace into my personal namespace, make some changes, and then create a merge request, the only users I see are me. I think it makes more sense to show all the users in gitlab-org. This is a regression caused by 1c2711f7.

### What are the relevant issue numbers?

Closes #1535

See merge request !682

Closes #1535

Changing your time zone

Added doc and link in workflow to how to change your time zone in Gitlab.

I used the following documents as reference. Please double check that the instructions I wrote are correct.
http://www.borngeek.com/2015/02/27/setting-the-time-zone-in-gitlab/
https://gitlab.com/gitlab-org/gitlab-ce/issues/443

I found that several users have this same issue, that they don't know how to change their time zone:
https://github.com/gitlabhq/gitlabhq/issues/5555
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/347
https://gitlab.com/gitlab-org/gitlab-ce/issues/56
http://jonathonreinhart.blogspot.com/2014/10/gitlab-time-zone-issues.html
http://stackoverflow.com/questions/5073917/why-doesnt-config-time-zone-seem-to-do-anything

See merge request !1827

Closes https://github.com/gitlabhq/gitlabhq/issues/6745

Fix Atom feeds.

Fixes #1643 and #1644.

See merge request !688

Work around a Chrome 43 bug preventing note editing

Fixes #1568 - and I mean "fixes"

I have no idea what causes this or why this fixes it and can't dig into it further right now, but the bug seems like a blocker so this needs to be fixed for 7.11.

See merge request !684

Update CHANGELOG with v7.10.4 changes

See merge request !662

Updated the gitlab_git gem

Moved changelog stuff to the correct release