Added note about backups for gitlab.com

Added note about backups for Gitlab.com based on question on Twitter
https://twitter.com/MarcelloLins/status/598544357294272513

See merge request !1828

Time zone text fix

Added small fix to /etc/gitlab/gitlab.rb

See merge request !1830

Keyboard shortcuts

Added doc about how to view keyboard shortcuts

cc/ @sytse

See merge request !1829

Use the user list from the target project in a merge request

### What does this MR do?

This MR derives the assignable users from the target project.

### Why was this MR needed?

In a merge request, the assignable users uses the list from the forked project, not the target project where the merge request will be going. For example, if I fork a project from the gitlab-org namespace into my personal namespace, make some changes, and then create a merge request, the only users I see are me. I think it makes more sense to show all the users in gitlab-org. This is a regression caused by 1c2711f7.

### What are the relevant issue numbers?

Closes #1535

See merge request !682

Closes #1535

Changing your time zone

Added doc and link in workflow to how to change your time zone in Gitlab.

I used the following documents as reference. Please double check that the instructions I wrote are correct.
http://www.borngeek.com/2015/02/27/setting-the-time-zone-in-gitlab/
https://gitlab.com/gitlab-org/gitlab-ce/issues/443

I found that several users have this same issue, that they don't know how to change their time zone:
https://github.com/gitlabhq/gitlabhq/issues/5555
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/347
https://gitlab.com/gitlab-org/gitlab-ce/issues/56
http://jonathonreinhart.blogspot.com/2014/10/gitlab-time-zone-issues.html
http://stackoverflow.com/questions/5073917/why-doesnt-config-time-zone-seem-to-do-anything

See merge request !1827

Fix Atom feeds.

Fixes #1643 and #1644.

See merge request !688

Work around a Chrome 43 bug preventing note editing

Fixes #1568 - and I mean "fixes"

I have no idea what causes this or why this fixes it and can't dig into it further right now, but the bug seems like a blocker so this needs to be fixed for 7.11.

See merge request !684

Update CHANGELOG with v7.10.4 changes

See merge request !662

Updated the gitlab_git gem

Moved changelog stuff to the correct release

**Why was this needed?**
The changes are pulled in 7.12.0 but where mistakenly put under 7.11.0

[skip-ci]
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Disabled expansion of top/bottom blobs for new file diffs

**What does this do?**
It updated the version of gitlab_git to the latest version

**Why is this needed?*
There was a bug in rugged (dependency of gitlab_git) that causes a segfault
error when seeding the database. That error has been fixed and the fix is in the
latest version of gitlab_git
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Customize the sanitization whitelist only once

Fixes #1651

See merge request !687

Fixes #1651

Use task_list fork to fix list items in notes

Closes #1645

See https://github.com/github/task_list/pull/60

See merge request !680

workaround for buggy lexers

It seems that some lexers can be buggy when used together with git blame.
This results in a 500 error when a user tries to open the blame page in some cases.
The workaround is pretty simple. Not only fall back to plaintext when the file content can't be guessed, but also when the lexer fails.

This closes #1521 and #1646

/cc @DouweM @JobV It would be awesome to have this in a patch release for 7.11 or even in the release. But that's probably to late.

See merge request !683