Element manager spike

So, moving away from the inheritance model, I came up with an `ElementManager`. It feels pretty good, and should be easy to use from JS as well as coffee. 

@nathansobo, would love a review + ideas. It's obviously a WIP as things will need to move around. Just trying to get a handle on what feels good for the general API.
Do we actually need the template to be on the DOM in this scenario? Seems like we could leave it detached. Seems to me the `template` tag actually being on the DOM is more of a convenience for HTML-oriented applications that need an in-page delivery mechanism for their templates. Since we're loading them from disk it shouldn't matter. Not sure how this interacts with Google's data binding stuff though.