Bower support

Submitting bower support for review and discussion.

From what I read on some of the Issues, the library is to be kept modular, and you include whichever part you want, so I added a bower.json to support such.

However, for the npm package all the modules were mixed in into the same namespace, so I want to open for discussion if a a concatenated underscore-contrib.js makes sense, and what approach would be preferred for the bower package.