update firebase example description

Author: yyx990803

source/examples/firebase.md

@@ -3,6 +3,6 @@ type: examples
 order: 2
 ---
 
-> This example uses [Firebase](https://www.firebase.com/) as the data persistence backend and syncs between clients in real time (you can try opening it in multiple browser tabs). In addition, it performs instant validation using Vue.js filters and triggers CSS transitions when adding/removing items.
+> This example uses [Firebase](https://www.firebase.com/) as the data persistence backend and syncs between clients in real time (you can try opening it in multiple browser tabs). In addition, it performs instant validation using computed properties and triggers CSS transitions when adding/removing items.
 
-<iframe width="100%" height="500" src="http://jsfiddle.net/yyx990803/2ok0hp6c/embedded/result,html,js,css" allowfullscreen="allowfullscreen" frameborder="0"></iframe>
+<iframe width="100%" height="500" src="http://jsfiddle.net/yyx990803/2ok0hp6c/embedded/result,html,js,css" allowfullscreen="allowfullscreen" frameborder="0"></iframe>