Update list.md (vuejs#1053)

Alex-Sokolov · chrisvfritz · commit c59979534eaf · 2017-07-31T10:06:35.000-04:00
* Update list.md

* Update list.md
diff --git a/src/v2/guide/list.md b/src/v2/guide/list.md
@@ -301,7 +301,7 @@ new Vue({
 ```
 
 {% raw %}
-<div id="todo-list-example">
+<div id="todo-list-example" class="demo">
   <input
     v-model="newTodoText"
     v-on:keyup.enter="addNewTodo"
