Enforce max line length

[TomSeldon]

We should enforce that the line length of the first line of the commit message (summary) should be <= 50 characters, and possibly that all subsequent line (description) should wrap at 72 characters.

More details on the 50/72 rule here: https://medium.com/@preslavrachev/what-s-with-the-50-72-rule-8a906f61f09c#.ns1unae7w