Add Create Merge Request buttons to commits page and push event.

Commits page:

![Screen_Shot_2015-05-09_at_22.27.09](https://gitlab.com/gitlab-org/gitlab-ce/uploads/f77c2e47f768b2fc132de6e3a2a0323e/Screen_Shot_2015-05-09_at_22.27.09.png)

Branches page:

![Screen_Shot_2015-05-09_at_22.55.24](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b0a6374f5c5d830ef19de9694e603c8f/Screen_Shot_2015-05-09_at_22.55.24.png)

Push event: (Only for new branches, and only shown to the pushing user)

![Screen_Shot_2015-05-09_at_22.27.21](https://gitlab.com/gitlab-org/gitlab-ce/uploads/989c9cb66ee03d09b96809452749d2b8/Screen_Shot_2015-05-09_at_22.27.21.png)

Push event with multiple commits and a Compare link:

![Screen_Shot_2015-05-09_at_22.28.01](https://gitlab.com/gitlab-org/gitlab-ce/uploads/a70c718e559f69177f9341c0af92707c/Screen_Shot_2015-05-09_at_22.28.01.png)

See merge request !632

Don't symbolize params.

See merge request !636

Migration Style Guide

Fixes #2305

See merge request !1821

Make omniauth-kerberos dependency optional (add group 'kerberos')

Follow shell command guidelines in Brakeman task

There is no real issue here because the shell command is completely
static, but it is still nicer to just follow the guidelines in
doc/development/shell_commands.md .

See merge request !1819

There is no real issue here because the shell command is completely
static, but it is still nicer to just follow the guidelines in
doc/development/shell_commands.md .

Don't show duplicate deploy keys

This fixes the issue described in [#1516](https://gitlab.com/gitlab-org/gitlab-ce/issues/1516) where you would see the same deploy key multiple times if it was used by multiple projects.

See merge request !629

Remove class and id attributes from SanitizationFilter whitelist

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2302

See merge request !631

Fix Firefox problems when it wants to render issuable component

Move project visibility from clone bar to repository details block for non empty project.

See merge request !1818

How to reset your root password

Added link and file correctly on Security doc.

Please review to make sure it's correct.

See merge request !1811

Added X-GitLab-Event header for web hooks

Adding quote_string to migration

See merge request !630

Fix link to the CI documentation

See merge request !627

Improved the backup documentation

See merge request !621

Use task_list gem for task lists

Task Lists can now be used in comments, and they'll render in previews. 👏

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2271

See merge request !599