Updated documentation for 7.5 release

Documentation for 7.5 release has been updated. Changes include:

- Pointed Ruby version in guides to 2.1.5
- Pointed gitlab-shell version in guides to 2.2.0

See merge request !1259

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

Conflicts:
	CHANGELOG

Update changelog

See merge request !1258

remove duplicate time zone entry in CHANGELOG

fix backup rake task

remove extra cd command

Run 'GC.start' after every EmailsOnPushWorker job

This change removed a lot of large peaks of the Sidekiq memory growth graph on gitlab.com.

See merge request !1257

Update gitlab_git to 7.0.0.rc11

See merge request !1256

Gitlab.com uses special packages, build them first

See merge request !1255

Author attributes clean

See merge request !1254

Strip tags from branch name

See merge request !1251

Update changelog

See merge request !1252

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

Fix for #8271: Correctly restore empty repositories.

If a project is being restored, but there is no bundle file, the project was
empty when it was backed up.  In this case, just use git init --base to create a
new bare repository.

Actions in the inbox

Related to #1607

See merge request !1247

RAM Requirements update

512MB of RAM is not enough to install using omnibus-gitlab.

Installation will fail in very random places.

Manual installation might also fail with this low amount of RAM.

See merge request !1249

Performance improvements

Push 1k commits cause 1k sql queries to collect commit author. But this variable was used only in 20 commits (from 1000).
So we did 980 sql queries without using it. This MR fixes it.

See merge request !1250

fixes the `block_removed_ldap_users` rake task

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

Custom git hook documentation

Merge branch 'commit-comments' of https://gitlab.com/jeroenj/gitlab-ce into jeroenj/gitlab-ce-commit-comments
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Conflicts:
	CHANGELOG

Drop all Postgres sequences during backup restore

See merge request !1226

Conflicts:
	CHANGELOG

In e23a26ae (and later 1bc99369) the API for Gitlab::LDAP::Adapter was
changed. I assume this rake task was an oversight in the refactoring of
the changed class.

While being on it, I noticed that already blocked users cannot be
blocked again.

Add issue edited timestamp

Comments already have this feature.
So, I think, issues should also have it.
![Снимок экрана 2014-11-08 в 17.07.10](https://gitlab.com/uploads/vernik91/gitlab-ce/4e87a15130/%D0%A1%D0%BD%D0%B8%D0%BC%D0%BE%D0%BA_%D1%8D%D0%BA%D1%80%D0%B0%D0%BD%D0%B0_2014-11-08_%D0%B2_17.07.10.png)

See merge request !235