Fix git blame syntax highlighting when different commits break up lines

### What does this MR do?

This MR fixes a bug where syntax highlighting would not work properly in certain lines when doing a `git blame` view of a file. Also, this MR reuses the Rugments lexer and formatter for each `git blame` commit block, which should make things faster and reduce overhead.

### Why was this MR needed?

When doing a `git blame`, GitLab feeds the Rugments lexer/formatter blocks of code based on the latest commit for each line.  However, this can cause lexer to fail because the state is cleared between each block of code, which causes `highlight` to fallback to the plaintext lexer. For example, notice this unhighlighted line in [this file](https://gitlab.common-lisp.net/cmucl/cmucl/blame/master/src/assembly/assemfile.lisp):

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b403fe5c2b883882a9eeea7e0409c583/image.png)

The fixed version looks like this:

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/32c4d7c8ff15a7d59b364dd988f7c657/image.png)

This MR requires a patch to rugments to allow the `continue` option to be passed to the lexer.

* https://github.com/rumpelsepp/rugments/pull/24
* https://github.com/rumpelsepp/rugments/pull/23
* Also submitted to rouge: https://github.com/jneen/rouge/pull/267

### What are the relevant issue numbers?

Closes #1521

See merge request !697

Some language improvements

Persist current merge request tab selection via URL

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2350

See merge request !728

Change some header icons

icons changed:

* profile settings: user icon to cog
* admin area: cogs to wrench

Based on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/719#note_1289290

![Screenshot_2015-05-27_17.58.12](https://gitlab.com/gitlab-org/gitlab-ce/uploads/762de4afb8ae229a96ead8b2d213b2a4/Screenshot_2015-05-27_17.58.12.png)

See merge request !726

Disable Unicorn::WorkerKiller in non-production environments

Addresses internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2281

See merge request !729

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2350

Closes #1521

Add ExternalLinkFilter to Markdown pipeline

Forces a `rel="nofollow"` attribute on all external links.

Addresses internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2314#note_46525

See merge request !727

Forces a `rel="nofollow"` attribute on all external links.

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

Fix milestone "Browse Issues" button.

After refactoring around issue/merge requests filters, the button stopped working :(

See merge request !699

Fix project snippets button appearing when it is disabled

There was a typo in 9bcd3639 that caused the project snippets option to be shown when it is disabled.

Closes #1705

See merge request !720

Fix clone URL losing selection after a single click in Safari and Chrome

### What does this MR do?

This MR deactivates the mouseup event in the `git clone` URL to prevent the text from being deselected after a single click.

### Why was this MR needed?

In Safari and Chrome 43.0.2357.65 (42.0.2311.152 worked fine), the URL would lose selection after a single click. To reproduce:

1. Go to https://gitlab.com/gitlab-org/gitlab-ce
2. Click on the URL in the repository (HTTP is selected by default).
3. Click on the SSH button.
4. Click on the URL again.

The URL selection should be selected automatically, but it is deselected immediately.

It appears that 92544df8 changed the selection event from `click` to `focusin` to make copy & paste work in X11. This Stack Overflow article discusses the deselection issue in detail:

http://stackoverflow.com/questions/3380458/looking-for-a-better-workaround-to-chrome-select-on-focus-bug

### What are the relevant issue numbers?

Closes https://github.com/gitlabhq/gitlabhq/issues/9326

See merge request !698

Add file attachment support in Milestone description

### What does this MR do?

This MR adds support for attaching files to Milestone descriptions.

### Why was this MR needed?

Dropzone support should be in every Markdown area. It seems that this one was overlooked.

### What are the relevant issue numbers?

Closes #1648

See merge request !712

Closes #1705

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

Move user avatar and logout button to sidebar

Related to https://dev.gitlab.org/gitlab/gitlabhq/issues/2272Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !719

Clarify navigation labels for Project Settings and Group Settings.

Addresses internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2337.

See merge request !703

Group project contributions by both name and email.

See https://twitter.com/Argorain/status/598751646143897600.

We now group by both name and email, so that "Douwe Maan - douwe@gitlab.com", "Douwe Maan - me@douwe.me" and "Douwe M. - me@douwe.me" are all combined into one graph.

Fixes internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2328.

See merge request !700

Prefix EmailsOnPush email subject with `[Git]`.

Fixes internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2112.

See merge request !701

Point people to the issue tracker on GitLab.com to prevent duplication.

/cc @jeroenvanbaarsen

See merge request !713

Add Accepted and Rejected tabs to MR lists.

Before, MRs were referred to as Merged or Closed, but the Merge button on the MR page read "Accept Merge Request", the activity feed even read "X accepted merge request Y", and the Closed tab on the MR index included both Merged _and_ Closed MRs. I've changed every occurrence to consistently refer to MRs as either Accepted or Rejected, which is less technical and more clearly two opposites.

![Screen_Shot_2015-05-25_at_17.02.31](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b0bf43aa1b5b9898a1c6b204dbcf669a/Screen_Shot_2015-05-25_at_17.02.31.png)

![Screen_Shot_2015-05-25_at_17.02.47](https://gitlab.com/gitlab-org/gitlab-ce/uploads/2ac05b1e1dba3b2d1692bd9242078f3a/Screen_Shot_2015-05-25_at_17.02.47.png)

![Screen_Shot_2015-05-25_at_17.03.03](https://gitlab.com/gitlab-org/gitlab-ce/uploads/4c0f0fa869c9130a6af18d80a1c6ebed/Screen_Shot_2015-05-25_at_17.03.03.png)

Addresses internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2201.

See merge request !702

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

Add to_reference method to referable models

Now there is a single source of information for which attribute a model uses to be referenced, and its special character.

See merge request !641

Add support for manually entering 2FA details

> ![Screen_Shot_2015-05-22_at_6.39.26_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/27b6cc0b2f88e0ccec234dd8d20db957/Screen_Shot_2015-05-22_at_6.39.26_PM.png)

Related to #1679 though I'm not sure if it entirely fixes it, since I don't have access to a Windows Phone.

See merge request !694

Add a note when an Issue or Merge Request's title changes

> ![Screen_Shot_2015-05-26_at_9.40.19_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/f05c6a7b9f489ce66560cfe724184ec9/Screen_Shot_2015-05-26_at_9.40.19_PM.png)

Closes #1434

See merge request !717

[ci skip]

Allow HipChat API version to be blank and default to v2

### What does this MR do?

This MR fixes a regression introduced in v7.11 that requires a HipChat API version to be specified when it is supposed to be optional.

### Why was this MR needed?

The "optional" HipChat API version in 57c72455 passed in a blank `api_version` when nothing was specified, and the code was not tested. This would cause a 500 Error.

### What are the relevant issue numbers?

Closes #772

See merge request !718

ADD: Note on how to setup dns hostname resolution to installation manual

Hi,

I'm suggesting to add the following note to the installation instructions. It took me some time to figure out why the test failed and why I wasn't able to push. The error messages did not point into the right direction so this might help other people with the same problems.

I hope my english is good enough, if not, please feel free to rephrase anything.

Thank you in advance,

Holger Segnitz

See merge request !236

Closes #772