[refactored] tossable.state$ to use the aggregator anyOf
[refactored] tossable.state$ to use the aggregator anyOf

Summary: I made `onStart` synchronous in D3325.  Since it's now synchronous, we can simplify `tossable.state$` to be the union of `spring.state$` and `draggable.state$`.

Reviewers: O2 Material Motion, O3 Material JavaScript platform reviewers, #material_motion, featherless

Reviewed By: O2 Material Motion, #material_motion, featherless

Tags: #material_motion

Differential Revision: http://codereview.cc/D3330

material-motion/material-motion-js,material-motion/material-motion-js,material-motion/material-motion-js