Review of 0.0.4 release

@addyosmani @ebidel & co.:

- Updated Polymer dependencies to 0.3.4.
- Added in basic tests.
- Refactored `demo.html` to use `<template is="auto-binding">`.
- Exposed a new "state" property for folks who would prefer that to listening for state change events. (Addresses https://github.com/GoogleWebComponents/google-youtube/issues/3)
- Renamed the events to match the convention used in other GWC projects.
That's in keeping with the way the previous events were setup. But you're right, I might as well switch the payload around to `e.data` since I'm making a breaking change to events anyway.