title: React checkedLink how to access value on change
body: <p>I am using React to write a simple component for a checkbox</p>
  
  <pre><code>&lt;input type="checkbox" checkedLink={this.linkState('checkedValue')} /&gt;
  </code></pre>
  
  <p>I cannot however figure out what code gets triggered on change of the checkbox value.  Am I supposed to retrieve the value onFocus or is there a better convention for retrieving the value after a change.</p>