[fixed] style prop on TransformTarget
The type signature for TransformTarget said it had a style prop, but there wasn't actually one implemented.
TransformTarget's primary use case is to be the child of AttachStreams - the couplet makes it easy to attach style streams to a DOM node in React. Since combineStyleStreams will emit the combined styles on each frame, TransformTarget ought to be able to accept that dictionary. This change enables that.
Tags: Material Motion
Differential Revision: http://codereview.cc/D3436