title: Extract/read React propTypes
body: <p>I want to visually test React components. The user can alter the component's props using a form. I would like to be able (for example) to render a <code>&lt;select&gt;</code> based on <code>React.PropTypes.oneOf(['green', 'blue', 'yellow'])</code>.</p>
  
  <p>When I read <code>MyComponent.propTypes</code> it returnes a function defined by React. Is there a way to extract/read the prop types?</p>