title: Angular 2 ngFor don't update data
body: <p>I have Component.</p>
  
  <pre><code>@Component({
  selector: 'todo-list',
  directives: [TodoItemRenderer],
  providers: [TodoService],
  template:
      '&lt;div&gt;'+
          '&lt;ul class="list-group"&gt;'+
              '&lt;li [(ngClass)]="item.class" class="list-group-item" *ngFor="#item of items"&gt;' +
                 '&lt;todo-item-renderer [todo] = "item"&gt;&lt;/todo-item-renderer&gt;'+
              '&lt;/li&gt;'+
          '&lt;/ul&gt;'+
      '&lt;/div&gt;'
  
  })
  </code></pre>
  
  <p>Also, this is the data I have in the service </p>
  
  <pre><code>items: TodoModel[] = [
      new TodoModel("sleep", "Completed"),
      new TodoModel("eat", "In progress"),
      new TodoModel("code", "In the plan")
  ];
  </code></pre>
  
  <p>When I add new element in this array </p>
  
  <pre><code>service.items,push(new TodoModel());
  </code></pre>
  
  <p>List doesn't update. What is the problem?</p>