title: Firebase update callback to detect error and sucssess
body: <p>How do I make this call back work? I have read the documents but I just cant figure it out for some reason?</p>
  
  <pre><code>   var ref = new Firebase("https://xxx.firebaseio.com/public/"+$scope.uid+"/shows/");
  var blast = ref.child(show_title);
  
  blast.update({
  "show_title": show_title,
  "show_image": show_image,
  "show_description": show_description,
  "show_email": show_email,
  "time": Firebase.ServerValue.TIMESTAMP
  });
  
   blast.update("I'm writing data", function(error) {
     if (error) {
      alert("Data could not be saved." + error);
    } else {
      alert("Data saved successfully.");
    }
  });
  </code></pre>