title: how to get sender in TouchableHighlight's onPress
body: <p>I have a list of Views, each View wrapped by TouchableHighlight, I bind a onPress handler for each Touchable</p>
  
  <pre><code>  ....
    &lt;TouchableHighlight onPress={this._preformTouchItem}&gt;
      &lt;View style={styles.item}&gt;
        &lt;Text&gt;{displayContent}&lt;/Text&gt;
      &lt;/View&gt;
    &lt;/TouchableHighlight&gt;
    ....
  
  _preformTouchItem(event) {
  }
  </code></pre>
  
  <p>I debug it in Chrome Dev Tools, the 'event' doesn't bind the 'sender' object, 
  How to know which View is clicked</p>