Moving to Bower, lots of cleanup

Removing/ignoring a lot of the product of a grunt build from the repo.
Adding Bower to manage third party JS libs.
Exceptions:
- we still have a custom build of Modernizr
- we check in require.js in built

*When you update your checkout:

./require.sh
npm install -g bower
npm install
bower install*

Very infrequently, bower install will need to be rerun. We'll let y'all know when that happens. It'll happen about as frequently as you need to do npm install, with the exception of the next few days as I continue to do this sort of work.