[fixed] NumericSpring to use current wobble API
[fixed] NumericSpring to use current wobble API

Summary: `normalizedVelocity` is no longer part of `wobble`.  However, since its `spring.stop()` bails if an animation isn't in progress, we should be able to safely delete this check (and let `stop` be called even when the spring is already stopped).

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/D3368

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