Remove combineReducers shortcut in favor of an explicit call

examples/counter/containers/App.js

@@ -1,6 +1,6 @@
 import React from 'react';
 import CounterApp from './CounterApp';
-import { createStore, applyMiddleware } from 'redux';
+import { createStore, applyMiddleware, combineReducers } from 'redux';
 import { Provider } from 'react-redux';
 import * as reducers from '../reducers';
 
@@ -13,7 +13,8 @@ function thunk({ dispatch, getState }) {
 }
 
 const createStoreWithMiddleware = applyMiddleware(thunk)(createStore);
-const store = createStoreWithMiddleware(reducers);
+const reducer = combineReducers(reducers);
+const store = createStoreWithMiddleware(reducer);
 
 export default class App {
   render() {

examples/todomvc/containers/App.js

@@ -1,10 +1,11 @@
 import React from 'react';
 import TodoApp from './TodoApp';
-import { createStore } from 'redux';
+import { createStore, combineReducers } from 'redux';
 import { Provider } from 'react-redux';
 import * as reducers from '../reducers';
 
-const store = createStore(reducers);
+const reducer = combineReducers(reducers);
+const store = createStore(reducer);
 
 export default class App {
   render() {

src/createStore.js

@@ -1,15 +1,7 @@
 import Store from './Store';
-import combineReducers from './utils/combineReducers';
 
-export default function createStore(
-  reducer,
-  initialState
-) {
-  const finalReducer = typeof reducer === 'function' ?
-    reducer :
-    combineReducers(reducer);
-
-  const store = new Store(finalReducer, initialState);
+export default function createStore(reducer, initialState) {
+  const store = new Store(reducer, initialState);
 
   return {
     dispatch: ::store.dispatch,