Theme Hook Alliance

I am working on an independent fork of _s to help my team (bourbon, neat, etc..). One thing that I love about the Genesis Framework is their robust hooks - which lead me to come across Doug Stewart's Theme Hook Alliance. I added them to my theme. I created a separate THA branch that only adds the THA functionality so it could be merged directly to _s if you choose. I saw an issue posted in January about it and the conclusion is that it would be considered. Here it is! This is my first github pull request.

Thanks, and Merry Christmas!