docs(bugfix):fix class name on todo list sample

fixes #880

public/docs/_examples/homepage-todo/ts/app/todo_list.ts

@@ -11,7 +11,7 @@ import {Todo} from './todo';
     }`
   ],
   template: `
-    <ul class="unstyled">
+    <ul class="list-unstyled">
       <li *ngFor="#todo of todos">
         <input type="checkbox" [(ngModel)]="todo.done">
         <span class="done-{{todo.done}}">{{todo.text}}</span>