never needed -ms- & -o-

They were just beta prefixes, never in production.  [Paul Irish removed](http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/) them as well.  I'm tempted to remove -moz- since that is [1% of browser share](http://caniuse.com/requestanimationframe).

Could [unroll the loop](https://github.com/cagosta/requestAnimationFrame/blob/master/app/requestAnimationFrame.js#L25-L29) also.