* added description
* simplified form
* enabled gfm autocomplete

Any mention of Issues, MergeRequests, or Commits via GitLab-flavored markdown
references in descriptions, titles, or attached Notes creates a back-reference
Note that links to the original referencer. Furthermore, pushing commits with
commit messages that match a (configurable) regexp to a project's default
branch will close any issues mentioned by GFM in the matched closing phrase.
If accepting a merge request would close any Issues in this way, a banner is
appended to the merge request's main panel to indicate this.

Show CI status even for closed MR. Use green bg for "Merged by username" message and red for closed one

Show the relation between Merge Requests and Mileston in different
places:
- Merge Request page
- Milestone list page
- Milestone details page

Didn't bother with files in db/, config/, or features/