[added] browser and module bundles
Previously, indefinite-observable.js was a script that wrote IndefiniteObservable to the global scope. Now, it's a module that exports IndefiniteObservable and imports symbol-observable.
The previous indefinite-observable.js has been replaced with indefinite-observable.bundle.js. It still inlines symbol-observable, but also exports IndefiniteObservable rather than writing to the global scope.
Tags: Material Motion
Differential Revision: http://codereview.cc/D3496