title: render html in state string
body: <p>I use setState to update part of the html but I found the new update html is not rendered. Here is the code, <a href="http://jsfiddle.net/5Y8r4/10/" rel="noreferrer">js fiddle</a>:</p>
  
  <p>html:</p>
  
  <pre><code>&lt;div&gt;hello&lt;br /&gt;world&lt;br /&gt;&lt;/div&gt;
  &lt;div id='content'&gt;&lt;/div&gt;
  </code></pre>
  
  <p>js:</p>
  
  <pre><code>var Main = React.createClass({
      getInitialState: function() {
          return {output: 'hello&lt;br /&gt;world&lt;br /&gt;'};
        },
      render: function() {
          return (
              &lt;div&gt;           
                  {this.state.output}
              &lt;/div&gt;
          );
          }
  });
  
  React.renderComponent(&lt;Main/&gt;, document.getElementById('content'));
  </code></pre>
  
  <p>I omit the part that update html from the server but the result is the same. How to let the string in state be rendered?</p>