Umbrella 2.0

[gaearon]

• (Breaking) Remove getReducer() from the Store public API (Remove getReducer() from Store API #668)
• (Breaking) Fix compose() to act like a normal compose() (Fix compose() to have a less surprising API #669)
• (Breaking) Rely on process.env.NODE_ENV being polyfilled (Rely on process.env.NODE_ENV being polyfilled #671)
• Release Redux 2.0
• Update React Redux to stop using getReducer() and release 2.0
• Update Redux DevTools to use Redux 2.0 and React Redux 2.0, update its examples, and release 2.0