This commit enables the usage of the Gitlab Markdown post processing
on all Markdown formatted files. For file types that do not contain
Markdown, it defaults to the Gollum native renderer to process the
content.

fixed commit title when commit message is an empty string and ensured that link_to_gfm helper doesn't break on nil body

Merge branch 'master' into non-interactive-aws-install

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

Also add hard_wrap option.

Makes use of 'extended' patterns to add comments to the groups, and also
reduces the total number of groups to just those that are used.

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