player sizing control

[jbenet]

Right now, player sizing is a mess.

content-view, splash-view, editor-view have heights defined in css, that are then overridden elsewhere (acorn website/player.html).

The desired scenario is that clients should only specify height on acorn-player, and the player should figure everything else itself.

This is of course tricky with things like the editor, or long form text, which could potentially take up a lot of height on the page (if desired). So clients should be able to omit height (maybe only specifying min-height), and player should resize its height accordingly.