Bumped Firebase version to upcoming 2.1.0 release

Author: Jacob Wenger

README.md

@@ -21,7 +21,7 @@ In order to use AngularFire in your project, you need to include the following f
 <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.7/angular.min.js"></script>
 
 <!-- Firebase -->
-<script src="https://cdn.firebase.com/js/client/2.0.6/firebase.js"></script>
+<script src="https://cdn.firebase.com/js/client/2.1.0/firebase.js"></script>
 
 <!-- AngularFire -->
 <script src="https://cdn.firebase.com/libs/angularfire/0.9.0/angularfire.min.js"></script>