[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.
Nit: This line is indented 3 spaces and the preceeding line has a `\` in it. The fjord code tends to do things like:

```
if (re.compile(...) and
        re.search(r' ...)):
```

in this situation.