Removed unneeded inner bind(this) (#122)

The inner bind is useless
create-react-apps 'default webpack config was what pointed out this issue.

Author: ShashankaNataraj

examples/todoApp/js/todoAppFirebaseExplicit.js

@@ -32,7 +32,7 @@ var TodoApp2 = React.createClass({
         var item = childSnapshot.val();
         item['.key'] = childSnapshot.key;
         items.push(item);
-      }.bind(this));
+      });
 
       this.setState({
         items: items