Move to JS

@thomasboyt @domenic @rpflorence @ebryn 

I think this is about ready to merge, I just wanted to have you guys give it a quick once-over. @thomasboyt is working on the esprima stuff (#24) starting with [this in-progress gist](https://gist.github.com/eventualbuddha/30d0a4dbfcf38b6ec245).