Demonstrates using Backbone events to communicate between view-controllers.
The main XML view consists of a TextField and two buttons, labeled "Fire Event" and "Remove Listener". When the user clicks "Fire Event" the required CustomView view-controller uses the Backbone library's
method to generate an event named someEvent. The event object includes a field named
message field that contains the text entered in the TextField.
The main application view-controller binds a callback function named handler to the
someEvent event, and displays the message enter in the TextField. It also provides a button that un-binds the handler from the same event.