Add button for toggling inline comments in diff view.

This is useful when there are many comments and they're becoming a distraction when trying to read the diff.
Merge branch 'toggle_diff_comments' of https://github.com/jacob-carlborg/gitlabhq into jacob-carlborg-toggle_diff_comments

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

Conflicts:
	app/assets/stylesheets/sections/commits.scss
	app/assets/stylesheets/sections/notes.scss
	app/views/projects/commits/_diffs.html.haml
	features/steps/project/merge_requests.rb
Correct BackgroundJobs page for both OSX and linux

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

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'master' of github.com:gitlabhq/gitlabhq