Don't force sliders to get evaluated on load. closes #1122

Squashed commit of the following:

commit d5957da3b282166c882c5d81e64936dec118ecf6
Author: David LaPalomento <dlapalomento@gmail.com>
Date:   Mon Mar 31 16:22:43 2014 -0400

    Peg the volume control to 1.0 on init
    Setup styles so that the volume control initially renders at full volume. This matches browser behavior where volume is available and saves Javascript from having to manually update the volume control on init. After the initial draw, the volume control is updated dynamically the same way it was before.

commit 8bc861fb861d4126f80fd11ed17d1f550498c559
Author: David LaPalomento <dlapalomento@gmail.com>
Date:   Wed Mar 12 17:16:30 2014 -0400

    Don't force sliders to get evaluated on load
    Since the load and play progress sliders are guaranteed to start from zero, set that through CSS. Calling Slider.prototype.update forces a re-flow because element dimensions are queried and style rules changed. That reflow consistently took around 60ms on my laptop which would mean dropped frames and "jerkiness" on initialization.
Updated volume slider to use ems intead of percent for default value clarity