Update README.md (#864)

updating Firebase Version in README.md

Author: idanb11

README.md

@@ -44,7 +44,7 @@ In order to use AngularFire in your project, you need to include the following f
 <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.8/angular.min.js"></script>
 
 <!-- Firebase -->
-<script src="https://www.gstatic.com/firebasejs/3.3.0/firebase.js"></script>
+<script src="https://www.gstatic.com/firebasejs/3.4.1/firebase.js"></script>
 
 <!-- AngularFire -->
 <script src="https://cdn.firebase.com/libs/angularfire/2.0.2/angularfire.min.js"></script>