title: unwind segue not work
body: <p>I add a an action method to view controller and Ctrl-Drag the button to Exit icon in storyboard,and the unwind segue is created successfully.But when I touch the button, the unwind segue doesn't work(the current scene doesn't navigate to original scene) and the action method isn't triggered.I don't know why.</p>
  
  <p>here is the action method</p>
  
  <pre><code>@interface HMCViewController2 : UIViewController
  -(IBAction)return:(UIStoryboardSegue *)segue;
  @end
  
  @implementation HMCViewController2
  ...
  -(IBAction)return:(UIStoryboardSegue *)segue{
  
  }
  
  @end
  </code></pre>
  
  <p>I upload the <a href="https://docs.google.com/file/d/0B0Ygk57VnimYQ3JoWW9RVUk2dlk/edit?usp=sharing" rel="noreferrer">project</a> to google drive.</p>