title: Listener for state changes in reactjs
body: <p>I have a component with a couple of input fields that updates the state of the component using the <code>valueLink={this.linkState('foo')}</code> facility provided by <code>React.addons.LinkedStateMixin</code>.</p>
  <p>Prior to this I was using the <code>onChange</code> handler to communicate the changes back to the server using a websocket connection, so I was wondering if I could replicate this behaviour somewhat and post the changes in the state back using a &quot;state change listener&quot; of some sorts?</p>