Switch back to rouge gem for synthax highlighting

Since gollum-lib blocks rouge from updating, let's bump the version
manually. The fix has already been accepted upstream:
https://github.com/gollum/gollum-lib/commit/9c042ea0914a7714abbda9d89e234c8a79fba893

This custom formatter for rouge is needed to generate HTML output
specifically for gitlab. Since its usecase is mostly suitable for
gitlab it had been rejected upstream:
https://github.com/jneen/rouge/pull/268

Thanks a lot to @stanhu, @jneen and @tsigo for review!

I have mainly created the rugments fork for the purpose of improving
gitlab's highlighting. Nowadays IMO it works way better than the old
highlight.js solution. But the development is stuck on my side because
of a couple of personal reasons:

  * I have finished my studies; last months I was writing my master
    thesis. So there was a huge time problem. I am sorry for that.

  * I had to move to Munich due to getting a (paid) job. Searching a
    flat here is horrible... :)

  * Last but not least, maintaining the same code base in two seperate
    projects is a mess.

I have decided to switch back to rouge due to several reasons:

  * In the beginning I was quite motivated, but since I start
    working on my new job next week, the best solution IMO is
    switching back to upstream rouge.

  * Rouge is continously improving:
    https://github.com/jneen/rouge/blob/master/CHANGELOG.md
    http://rouge.jneen.net/

  * There should be absolutely no regressions with this change. Most
    likely this pull request will almost fix some minor bugs.

  * One less gem in gitlab is a good thing. since Gitlab is quite a
    huge bundle of gems. Reducing complexity should be a major
    milestone.

Thanks a lot to @stanhu and @jneen for the review!

Make `hr`s more visible in note bodies

Closes #2107

See merge request !1054

Fix bug causing Bitbucket importer to crash when OAuth application
had been removed.

Fixes gitlab-com/support-forum#241.

See merge request !1057

Change before(:all) -> let! to avoid leaking data across tests

Closes https://github.com/gitlabhq/gitlabhq/issues/9495

See merge request !1061

Closes https://github.com/gitlabhq/gitlabhq/issues/9495

Upgrade gitlab_git to version 7.2.6 to fix 500 Error when creating network graphs

See merge request !1060

Closes #745

Added a timestamp to the wikis page just below the title

Now it looks like this:

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/813f85496db915cf14ee223c8b15478f/image.png)



See merge request !1055

New document in GitLab Basics about adding new files



See merge request !1913

Added info about repo size

Because of tweet https://twitter.com/s_hulard/status/624160758335672320

See merge request !1912

Return comments in created order in merge request API

Closes #1832

See merge request !985

Fix commit data retrieval when branch name has single quotes

Quotes in ref names need to be escaped properly in JavaScript.

Closes #1724

See merge request !1046

Render Note field hints consistently for "new" and "edit" forms

- The "Edit" form didn't have Markdown hints.
- The "New" form had a paperclip icon for attachments, the "edit" form
  didn't.

Closes #2010

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2525

See merge request !1049

Closes #2107

Added note about SSH keys being unique

Because of issue https://gitlab.com/gitlab-com/support-forum/issues/143

See merge request !1914

Add rake task 'gitlab:update_commit_count'

Starting with migration `20150717130904` commit count is stored in the
database. For existing projects it defaults to `0` and is updated to the
correct value when commits are pushed.

The newly introduced rake task updates the commit count for all projects
which have not been updated yet.

![gitlab-rake-update-commit-count](https://gitlab.com/gitlab-org/gitlab-ce/uploads/4785009e0f3fc4c3199fe65dfb8e60e0/gitlab-rake-update-commit-count.png)

Refs !986, !989, #2040, #2089.

See merge request !1040

Create project services on Project creation

Closes internal https://dev.gitlab.org/gitlab/gitlab-ee/issues/306#note_53354

See merge request !1045

- The "Edit" form didn't have Markdown hints.
- The "New" form had a paperclip icon for attachments, the "edit" form
  didn't.

Closes #2010

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2525

Fix live notes refresh in relative URL deployments

### What does this MR do?

This MR fixes URLs used for refreshing notes--the relative_url prefix was appended twice

### Why was this MR needed?

In case of `relative_url` installation, opening a page which does refresh notes (i.e. merge request), the page generates lots of 404 errors in the browser console. It turns out that the relative_url is prepended to the link twice.

Supersedes !233

See merge request !1048

Closes #1724

Fix the "Reload with full diff" URL button

On the first load, the merge request tabs would be requested in JSON format to render
the HTML. This would cause the "Reload with full diff" button to create a link to `diff.json`. Instead, generate the path in HTML mode.

Closes #2041

See merge request !1019

Dynamically check `:admin_*` ability in two more spots.

Closes #2092 

Depends on !1037 

See merge request !1042

Fix error 500 when no HEAD is available

Steps to reproduce:

1. Create a project with a README
2. In the actual remote, type: `git symbolic-ref HEAD refs/heads/nowhere`
3. Check that HEAD is gone via `git ls-remote .`
4. Go to the projects page and see the Error 500

Error:

```
NoMethodError - undefined method `sha' for nil:NilClass:
  app/helpers/projects_helper.rb:281:in `readme_cache_key'
  app/views/projects/_readme.html.haml:10:in `_app_views_projects__readme_html_haml___2036282917939462960_70154565285700'
  actionview (4.1.11) lib/action_view/template.rb:145:in `block in render'
  activesupport (4.1.11) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.1.11) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.1.11) lib/active_support/notifications.rb:159:in `instrument'
  actionview (4.1.11) lib/action_view/template.rb:339:in `instrument'
  actionview (4.1.11) lib/action_view/template.rb:143:in `render'
  rack-mini-profiler (0.9.0) lib/mini_profiler/profiling_methods.rb:108:in `block in profile_method'
  actionview (4.1.11) lib/action_view/renderer/partial_renderer.rb:306:in `render_partial'
  actionview (4.1.11) lib/action_view/renderer/partial_renderer.rb:279:in `block in render'
  actionview (4.1.11) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
  activesupport (4.1.11) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.1.11) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.1.11) lib/active_support/notifications.rb:159:in `instrument'
  actionview (4.1.11) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
  actionview (4.1.11) lib/action_view/renderer/partial_renderer.rb:278:in `render'
  actionview (4.1.11) lib/action_view/renderer/renderer.rb:47:in `render_partial'
  actionview (4.1.11) lib/action_view/helpers/rendering_helper.rb:35:in `render'
  haml (4.0.5) lib/haml/helpers/action_view_mods.rb:10:in `block in render_with_haml'
  haml (4.0.5) lib/haml/helpers.rb:89:in `non_haml'
  haml (4.0.5) lib/haml/helpers/action_view_mods.rb:10:in `render_with_haml'
  app/views/projects/show.html.haml:47:in `_app_views_projects_show_html_haml__1458303859692972698_70154948164180'
  actionview (4.1.11) lib/action_view/template.rb:145:in `block in render'
  activesupport (4.1.11) lib/active_support/notifications.rb:159:in `block in instrument'
```

Closes https://github.com/gitlabhq/gitlabhq/issues/9484, but there may be some other issue there.

See merge request !1041

Add admin_merge_request ability to Developer level and up

This was necessary because this permission is checked dynamically by
`app/views/shared/issuable/_context` when on a Merge Request.

Closes #2058

See merge request !1037

Closes #2092

Closes #2092