[bug 1108755] Add a git commit message linter

As mentioned in the comments of bug 1108755 as requirements,
the commit message linter does the following things:

1. Enforces max. 79 characters per line
2. Verifies the summary line has bug numbers in the right format
3. Does a bugzilla lookup for the bug and prints out the 'bug id',
   'summary' and 'assigned to' fields.
This is perfect. We definitely don't want this to bail if you're doing work while not connected. Awesome job here!