title: Adding a Back button to a iOS app in Titanium Appcelerator without TabGroup or NavBar
body: <p>I'm developing with Titanium Appcelerator for iOS. I would like to manage manually a 'back' button using the properties of window, that can set a left and right buttons.</p>
  
  <p>I'm trying with this code:</p>
  
  <pre><code>var win = Titanium.UI.currentWindow;
  win.backgroundColor = '#FFF';
  var b = Titanium.UI.createButton({title:'Back'});
  win.setLeftNavButton(b);
  b.addEventListener('click', function()
      {
      win.close();
    });
  </code></pre>
  
  <p>But no button is showed.</p>