requestAnimationFrame()

[cerebrl]

@joshnh After some reading and research, I think we should probably start using requestAnimationFrame() to our newly developed JS components that need to kick off any CSS animation. Right now, we are using setTimeout(), but that's kind of a hack.

@NateJackman Since requestAnimationFrame() is not IE9- compatible, we should probably create a "polyfill" for it with phi-dom. We can easily have it fallback to setTimeout();

Thoughts?