Fix old @mount in todo example

Author: rush

examples/todomvc.html

@@ -132,7 +132,7 @@
   }).mount('#app')
 </script>
 
-<div id="app" @mounted="setupRouting" v-effect="save()" v-cloak>
+<div id="app" @vue:mounted="setupRouting" v-effect="save()" v-cloak>
   <section class="todoapp">
     <header class="header">
       <h1>todos</h1>