Core module in coffeescript?

@occ would really like to use coffeescript, so I figured we could actually have the core src/shield.js done in coffee. I mostly care about the api, not soo much the internal normalization stuff. Plus tracekit is ugly and whoever deals with it should have their choice of language. I don't think it will be hard to hack coffeescript2 to support function names in the near or far future.
