Update rerun to remove celluloid as dependency

After sidekiq 4 migration, we no longer need celluloid. `rerun` recent version also removed it from its dependency, so by getting this MR merged, we can solve #3797 

See merge request !2088

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Link to correct (source) project on MR builds tab

Used to link to `gitlab-org/gitlab-ce/commits/<branch-name>`, now links to correct project.

See merge request !2115

Temporarily disable Markdown caching



See merge request !2120

Fix headers of milestone and snippet show pages

Fix layout, and move "Edit" button to very right just like issue/MR.

Before:

![Screen_Shot_2015-12-15_at_17.33.20](/uploads/dbbeb6868b80e21894159126a0feca6a/Screen_Shot_2015-12-15_at_17.33.20.png)

![Screen_Shot_2015-12-15_at_17.33.28](/uploads/53d10b42adc34e48b063889120e9a746/Screen_Shot_2015-12-15_at_17.33.28.png)

After:

![Screen_Shot_2015-12-15_at_17.34.25](/uploads/b0d0ea3f6a7b61d51b474419207f7a02/Screen_Shot_2015-12-15_at_17.34.25.png)

![Screen_Shot_2015-12-15_at_17.35.55](/uploads/65b922f5249655d3733740690577c9d7/Screen_Shot_2015-12-15_at_17.35.55.png)

cc @skyruler 

cc @rspeicher 8.3 please!

See merge request !2104

Only cache markdown when object has been saved and has a proper cache_key.

See merge request !2119

Fix 'Merge Immediately' button

Fixes #4125

See merge request !2117

Fix bad merge

/cc: @dzaporozhets 

See merge request !2116

Fix endpoint not setting needed @ci_commit

/cc @DouweM

See merge request !2112

Fix right margin of control list

Before:

![Screen_Shot_2015-12-16_at_16.29.39](/uploads/7a6aa79b6af0900d9257ce86ab822a22/Screen_Shot_2015-12-16_at_16.29.39.png)

After:

![Screen_Shot_2015-12-16_at_16.29.45](/uploads/d52fdc70ecd63fc61ae6ae87b3b7d1a5/Screen_Shot_2015-12-16_at_16.29.45.png)


See merge request !2114

Issuable sidebar tweaks

- Move cross-project reference down 
- ~~Fix "Notifications" label color~~ Reverted
- ~~Use regularly colored button for "Subscribe"/"Unsubscribe"~~ Reverted

Before:

![Screen_Shot_2015-12-15_at_17.38.08](/uploads/d4eeab44bb21fca2fe9ebe620ed9e060/Screen_Shot_2015-12-15_at_17.38.08.png)

After:

(Only the moved cross-project reference is still relevant, other changes have been reverted)

![Screen_Shot_2015-12-15_at_17.38.23](/uploads/b61aed3a0884c986785a5b09af8dbb25/Screen_Shot_2015-12-15_at_17.38.23.png)

cc @skyruler 

cc @rspeicher 8.3 please!

See merge request !2105

Fix double right border in MR discussion
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

# Before
![Screenshot_2015-12-16_15.44.00](/uploads/dd2c85e82fdb784e897cf1a695af1a1e/Screenshot_2015-12-16_15.44.00.png)

# After
![Screenshot_2015-12-16_15.43.36](/uploads/b50954e01bb3f45d2df6f43d34a1db60/Screenshot_2015-12-16_15.43.36.png)

cc @skyruler 

See merge request !2113

This reverts commit e4e1777a.

This reverts commit c1db8d15.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Revert "Make sure notify email always has author info."

This reverts commit 303f79f8.

See merge request !2103

Pass all requests from NGINX to gitlab-workhorse



See merge request !2073

Fix clipboard buttons on MR instructions and Commit#show



See merge request !2108

Add SVN to Git migration documentation

Document the process of migrating a SVN repository and pushing it to GitLab.

cc/ @axil

See merge request !2028

Fix time_ago_with_tooltip for activity feed

Closes #4002

See merge request !2074