Bump gitlab_git version to 6.2.2 for 7.3

We need to bump the gitlab_git version for 7-3-stable to 6.2.2 so that it includes the 0.21.2 version of rugged.

QA Tests have been performed to warrant compatibility.

/cc @jacobvosmaer @job

See merge request !1377

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

This conmmit fixes wierd behaviour when you see wrong comments about new
commits in merge requests.

Short explanation of a bug:
When you push new commits to project we updated `project.merge_requests`
with comment about push. But `project.merge_requests` includes also
merge requests from forks to origin project. So when you push to master
branch it commented on all merge requests from forks to origin where
source_branch was `master`

Conflicts:
	doc/install/installation.md

Revert sticky headers

See merge request !1104

This reverts commit 6eb85b1a.

Save last scrollposition and scroll back when leaving ZEN mode

improve 7.3 upgrade process & redis setup

update gitlab shell to 1.9.8 for gitlab 7.2.2

Typo it -> its.

formatting improvements to 6.0-to-7.3.md

Fixes
https://github.com/gitlabhq/gitlabhq/commit/2b35c887904b6a7a05a7c88fdf1ccd66ba943e20#commitcomment-7829537,
https://github.com/gitlabhq/gitlabhq/commit/5704e6fee9d2dea67c4a91b43d06a9958484d29b#commitcomment-7829367,
&
https://github.com/gitlabhq/gitlabhq/commit/5704e6fee9d2dea67c4a91b43d06a9958484d29b#commitcomment-7829381

As committed in https://github.com/gitlabhq/gitlabhq/commit/873acfd9aa54e801d5786c32b05c4f8ad21af72a GitLab 7.2.2 requires GitLab Shell 1.9.8. Fixes https://github.com/gitlabhq/gitlabhq/issues/7806.

Prevent default action when closing zen mode

Factor zen mode.

Adds support for ruby 1.8 in webhook example

By using the hash rocket syntax, the web hook will work on older versions of ruby (1.8) in addition to 1.9, 2.0 ect..
Moves do .. end to separate lines for ruby-lint.

Additional Information:
http://stackoverflow.com/questions/25899476/webrick-gives-error-unexpected-expecting-end
https://github.com/spuder/r10k_gitlab_webhook