title: Getting a.ref is not a function error when upgraded to angularfire 1.2
body: <p>Following codebase used to work with firebase 2.3.1 and Angularfire 1.1.3</p>
  
  <pre><code>Var fb = new firebase("https://database name.firebaseio.com");
  
  var fbObj = $firebaseObject(fb.child("users/" + userId));
  </code></pre>
  
  <p>I upgraded to firebase3.0 and Angularfire 1.2. </p>
  
  <p>As a result, here is how the above code got modified:</p>
  
  <pre><code>var config = {/* ...  */};
  firebase.initializeApp(config);
  var fb = firebase.database().ref();
  
  var fbObj = $firebaseObject(fb.child("users/" + userId))
  </code></pre>
  
  <p>The above code however threw error such as a.ref is not a function when instantiating fbObj.</p>
  
  <p>Please suggest.</p>