title: Calling the setTitle method on an NSMenuItem object is not changing the displayed title, but is changing the property
body: <p>Using MacRuby with XCode, I would like to be able to change the title of an item in my application's menu.</p>
  
  <p>In my simplified example I have window with a button and a label, and a menu with a menu item in it.</p>
  
  <p>I created the following class and linked @my_label to the label, @my_menu to the menu item, and the button click to the button_clicked method.  When you click on the button, the text of the label update to show "Someone pushed the button", but the actual displayed title of the menu is not changing.</p>
  
  <pre><code>class MyWindowController &lt; NSWindowController
      attr_accessor :my_label
      attr_accessor :my_menu
  
      def button_clicked(sender)
          @my_menu.setTitle("Someone pushed the button")
          @my_label.stringValue = @my_menu.title
      end
  
  end
  </code></pre>
  
  <p>This would seem to indicate that the <code>title</code> <em>property</em> is being updated, but the change just isn't being shown.</p>
  
  <p>I've looked at the docs for NSMenuItem and I can't see anything obvious that I'm doing wrong. However I'm pretty new to this so hopefully I'm just missing something simple.</p>
  
  <p>I'm using MacRuby 0.10 with XCode 4 if that makes any difference.</p>
  
  <p>Paul </p>