title: Click event on tree's children/node
body: <p>I really confused by ExtJs tree object, something is wrong with my code but I don't know what. </p>
  
  <p>Consider I have this code:</p>
  
  <pre><code>var store = Ext.create('Ext.data.TreeStore', {
      root: {
          expanded: true,
          children: [
              { text: "detention", leaf: true },
              { text: "homework", expanded: true, children: [
                  { text: "book report", leaf: true },
                  { text: "alegrbra", leaf: true}
              ] },
              { text: "buy lottery tickets", leaf: true }
          ]
      }
  });
  
  Ext.create('Ext.tree.Panel', {
      title: 'Simple Tree',
      width: 200,
      height: 150,
      store: store,
      rootVisible: false,
      renderTo: Ext.getBody()
  });
  </code></pre>
  
  <p>How can I bind a <strong>click</strong> event to my tree's children/leaf?</p>