Upgrade React-Redux (2nd attempt)

Summary:
- Update and include `react-redux` to Greenkeeper
- Remove legacy context which is used to access `store`
- Export `store` directly to use instead of legacy context

Note:
1st attempt: D18169584 -> got backouted in D18203354

Reviewed By: jknoxville

Differential Revision: D18297298

fbshipit-source-id: fd968f1b211eabb094113a0b35e84305f70117fc

src/init.tsx

@@ -32,7 +32,7 @@ import {setPersistor} from './utils/persistor';
 import React from 'react';
 import path from 'path';
 
-const store = createStore<StoreState, Actions, any, any>(
+export const store = createStore<StoreState, Actions, any, any>(
   reducers,
   window.__REDUX_DEVTOOLS_EXTENSION__
     ? window.__REDUX_DEVTOOLS_EXTENSION__({