Enhancement: Allow multiple animations per element

[bringking]

The spec allows multiple animations to be applied to each element (see here for example -http://danielcwilson.com/blog/2015/08/animations-part-3/). The current structure only allows for a single set of keyframes/timing per element.

Implement something like -

<Animated.div keyframes={[[...],[...]]} timing={[[...],[...]]}></Animated.div>