Batch morphs

[joeldrapper]

After #21, Morphlex will morph within an animation frame so the browser doesn't waste time rendering the DOM as it’s going through continuous transformations. I think we can extend this further with a “batch morphing” interface that wraps multiple morphs in a requestAnimationFrame callback. This would be especially useful for Phlex.js, where we might request a dozen fragments from the server and morph them all.