title: "backbutton" event won't fire
body: <p>I am attempting to build a phonegap app for Windows Phone 7. I am trying to follow the documentation for the "backbutton" event (http://docs.phonegap.com/en/2.0.0/cordova_events_events.md.html#backbutton), but I can't seem to get it to work.</p>
  
  <p>The "deviceready" event fires, but the "backbutton" event does not. When compiling and running in Visual Studio Windows Phone emulator the onDeviceReady function is called and "Device ready" is logged, but when the emulator back button is pressed the application exits and nothing is logged in the console. 
  When the back button is pressed the OnBackKeyDown function should run.</p>
  
  <p>copy of the code from the offical doc:</p>
  
  <pre><code>&lt;html&gt;
      &lt;head&gt;     
          &lt;script type="text/javascript" charset="utf-8" src="cordova-2.0.0.js"&gt;&lt;/script&gt;
          &lt;script type="text/javascript"&gt;
              function onLoad() {
                  document.addEventListener("deviceready", onDeviceReady, false);
              }
              function onDeviceReady() {
                  console.log("Device ready");
                  document.addEventListener("backbutton", onBackKeyDown, false);
              }
              function onBackKeyDown() {
                  console.log("Back button pressed");
              }
          &lt;/script&gt;
      &lt;/head&gt;
      &lt;body onload="onLoad()"&gt;
          &lt;div&gt;&lt;/div&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>