Add an official license/terms of use to the top of the .h/.cpp files.

[jrlanglois]

Something regarding the license of the repo: https://github.com/nick-thompson/blueprint/blob/master/LICENSE.md

This is just a suggestion! I haven't a clue about the validity or usefulness.

[nick-thompson]

Yea I think this is a great idea, and certainly makes more sense than the headers you mention in #161 :D