title: React extends class using ES5
body: <p>It's ES6 syntax, that work OK for me:</p>
  
  <pre><code>import {Component} from 'react';
  class A extends Component {}
  class B extends A {
      // I can redeclare some methods here
  }
  </code></pre>
  
  <p>And how implement this with ES5? I mean:</p>
  
  <pre><code>var React = require('react');
  var A = React.createClass({});
  var B = ???
  </code></pre>
  
  <p>Could someone provide some example, please?</p>