title: redux replaceReducer seems not work in HMR
body: <p>
  I've configured a development environment with <code>react-hot-loader</code>. <code>HMR</code> is working normally and I've added the configuration below for <code>redux</code>
  </p>
  
  <pre><code>if (module.hot) {
     // Enable Webpack hot module replacement for reducers
     module.hot.accept('../reducers', () =&gt; {
       console.log('reducers change')
       const nextReducer = require('../reducers').default
       store.replaceReducer(nextReducer)
    })
  }
  </code></pre>
  
  <p>
  when I change the reducer file, <code>module.hot.accept</code> handler works and [HMR] seems to get the succeess info</p>
  
  <pre><code>[HMR] connected
  [HMR] bundle rebuilding
  [HMR] bundle rebuilt in 405ms
  [HMR] Checking for updates on the server...
  reducers change
  [HMR] Updated modules:
  [HMR]  - ./src/reducers/testReducer.js
  [HMR]  - ./src/reducers/index.js
  [HMR] App is up to date. 
  </code></pre>
  
  <p>
  but the state is not changing, it's value is still the initial one.</p>