New branch button on issues

Creates a button which creates a branch for you, referencing the original issue in the branch name. When creating the MR the text `Closes #iid` is appended to the description field.

The button; with styling

![Screenshot_from_2016-02-13_17-28-54](/uploads/9595fbfef88c10a499829beaa3db11c1/Screenshot_from_2016-02-13_17-28-54.png)

Links to the related branches on the issue

![Screenshot_from_2016-02-13_17-31-48](/uploads/ee7a78754eb5e2389f8671771bb59af9/Screenshot_from_2016-02-13_17-31-48.png)

Styled like the MR links

![Screenshot_from_2016-02-13_17-31-53](/uploads/c60130333a650a16f51b014aeb1458c3/Screenshot_from_2016-02-13_17-31-53.png)


Please provide input on the following; the CI repo on the GDK had the following happening with the current way I implemented the matching:

![Screenshot_from_2016-02-14_08-57-19](/uploads/35e7a3687a0fa801aba1ad66305ab2ff/Screenshot_from_2016-02-14_08-57-19.png)

Closes #3886 

cc @DouweM 


See merge request !2808

Fix horizontal overflow that occurs in the code tag

closes #14167 

### Before Fix
![Screen_Shot_2016-03-16_at_9.10.52_PM](/uploads/b4a282ffc33684983d7e2482b8e13a8f/Screen_Shot_2016-03-16_at_9.10.52_PM.png)

### After Fix
![Screen_Shot_2016-03-16_at_9.11.16_PM](/uploads/8acca3b46bfdbd929cc096ad070022e2/Screen_Shot_2016-03-16_at_9.11.16_PM.png)


See merge request !3255

Follow the CSS Style Guide rules for including a space after the property colon.

Fixes violations of SpaceAfterPropertyColon.

Discussed in #14299.

[ci skip]

cc: @rspeicher @jschatz1 

See merge request !3260

Reuse `no_cache_headers` method in badges controller

Closes #14100

See merge request !3269

Spinach was right, I was a fool..

Fix typo in README.md



See merge request !3250

Fix wiki search results point to raw source

Closes https://github.com/gitlabhq/gitlabhq/issues/9581

See merge request !3138

Fixes violations of SpaceAfterPropertyColon.

Discussed in #14299.

[ci skip]

Follow the CSS Style Guide rules for unitless zero values.

Discussed in #14299.

cc: @rspeicher @jschatz1 

See merge request !3259

Updated Emoji Rake task to conform to style guide.

Discussed in #14299.

[ci skip]

omniauth-auth0 gem support

See merge request !3246

Fixes issue with dropdown caret being incorrect color

Previously:

![Screen_Shot_2016-03-16_at_19.31.20](/uploads/b887a7b8249f172513c68289c52a4cf7/Screen_Shot_2016-03-16_at_19.31.20.png)

Now:

![Screen_Shot_2016-03-16_at_19.29.37](/uploads/9c0d6a3002c18a8c7890df8dce612dcb/Screen_Shot_2016-03-16_at_19.29.37.png)



See merge request !3254

See merge request !3249

Follow the CSS Style Guide rules for HEX colors.

Use lowercase letters and shorthand values for HEX colors where possible, in accordance with the CSS Style Guide.

Discussed in #14299.

\cc @jschatz1 @rspeicher

See merge request !3238

Install Git 2.7.3, not 2.4.3



See merge request !3248

On PostgreSQL the index is created concurrently.

Fixes gitlab-org/gitlab-ce#14325

Fix requirements.md link and improve PostgreSQL commands

 - Point requirements.md link to the correct location

 - Link to gitlab installation.md document instead of github

 - Use psql command switch to run specified SQL commands for creation of user and database permissions.
    -  Instead of requiring a comment like `# Do not type the 'template1=#', this is part of the prompt` it may be easier to just use the command switch with `psql` to execute the SQL commands.


*forgot [ci skip] :(*

See merge request !3176

Return an empty Array when there aren't lines to parse.

Fixes #14306

See merge request !3243

Support Wiki with UTF-8 page name

## What does this MR do?

Support Wiki with UTF-8 page name.

See https://github.com/gollum/gollum/pull/929

## Why was this MR needed?

Relax constraints for wiki slug in aac65984.

It allows to create a wiki with UTF-8 name, but creating a wiki with UTF-8 name causes 500 error.

Creating a wiki with UTF-8 name once, then creating or updating wiki with ascii name also cause 500 error i.e. no one can create and update any wiki pages in the project.

## Workaround

1. Go to `https://DOMAIN/repo/wikis/git_access` -> this page display the link to git clone
2. Clone the wiki repo
3. Find the page with UTF-8 name
4. Rename or Delete these files
5. Commit and push

## What are the relevant issue numbers?

- #13979
- #13891
- #13698
- #13603
- #13317
- #12906
- #12825
- #10945 

## Todo

- [x] Waiting for 'gollum-rugged_adapter' that support rugged v0.24.0 release

'gollum-rugged_adapter' gem doesn't allow to install rugged v0.24.0 (it's still beta version),
but 'gitlab_git' gem depends on rugged v0.24.0b13.

So it can't install both 'gollum-rugged_adapter' and 'gitlab_git' now.


See merge request !2999

A worker deletes a user, so the request doesn't time out

Fixes #13261


See merge request !2855

Fix Capybara 2.6.2 deprecation warnings

See merge request !3236

Bump Git version requirement to 2.7.3

[ci skip]

See merge request !3240

The feature spec now also tests the absence of the new branch button

Fixes label on "Assignee" dropdown

Fixes #14301 

See merge request !3239