Add comments on the side-by-side diff.
Remove unecesarry array operations.
Move organizing of comments to helper.
Add one feature test.
Fix diff_helper spec.
Merge branch 'implement_comments_on_parallel_diff' into 'master'

Implement comments on parallel diff

Fixes #1565

See merge request !1090
Merge branch 'master' of github.com:gitlabhq/gitlabhq