old_contents: // import ReactDom from 'react-dom'
  
  // ReactDom.render((
  // 	<div>
  // 	<p>hello world</p>
  // 	</div>
  // ) , document.getElementById('app'));
  
  
  var React = require('react');
  var ReactDOM = require('react-dom');
  
  
  class Hello extends React.Component {
    render() {
      return <h1>Hello world</h1>;
    }
  }
  
  ReactDOM.render(
    <Hello />,
    document.getElementById('app')
  );
new_contents: // import ReactDom from 'react-dom'
  
  // ReactDom.render((
  // 	<div>
  // 	<p>hello world</p>
  // 	</div>
  // ) , document.getElementById('app'));
  
  import mui from 'material-ui';
  // let MenuItem = mui.MenuItem;
  // let LeftNav = mui.LeftNav;
  let RaisedButton = mui.RaisedButton;
  
  var React = require('react');
  var ReactDOM = require('react-dom');
  
  
  class Hello extends React.Component{ 
    render() {
      return <h1>Hello world</h1>;
    }
  }
  
  ReactDOM.render(
    	<div>
  	  <Hello />
  	  <RaisedButton label="hello" primary={true}/>
    	</div>
    ,
    document.getElementById('app')
  );
subject: add material-ui