requestAnimationFrame for 2014

Never needed [ms or o prefixes](http://dev.opera.com/articles/view/better-performance-with-requestanimationframe/) for released browsers.  Even [Paul Irish](http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/) dropped them.  Very rarely need [moz prefix](http://caniuse.com/requestanimationframe), so that is included, but commented out by default.

Therefore, don't need a prefix loop either.

Moved `var lastTime = 0;` inside the `else` fallback (about 15% of browsers); does not need to be global.