Implement Redux DevTools extension

Author: zalmoxisus

examples/counter/store/configureStore.js

@@ -5,6 +5,7 @@ import reducer from '../reducers';
 export default function configureStore(initialState) {
   const finalCreateStore = compose(
     applyMiddleware(thunk),
+    window.devToolsExtension ? window.devToolsExtension() : f => f
   )(createStore);
 
   const store = finalCreateStore(reducer, initialState);

examples/todomvc/store/configureStore.js

@@ -2,7 +2,7 @@ import { createStore } from 'redux';
 import rootReducer from '../reducers';
 
 export default function configureStore(initialState) {
-  const store = createStore(rootReducer, initialState);
+  const store = (window.devToolsExtension ? window.devToolsExtension()(createStore) : createStore)(rootReducer, initialState);
 
   if (module.hot) {
     // Enable Webpack hot module replacement for reducers