title: Detect changes on NSUserDefaults with suiteName
body: <p>I created appGroups and did set up a <code>NSUserDefaults</code> using that group. I have a observer for which is not triggered when the value is changed. </p>
  
  <pre><code>let defaults = NSUserDefaults(suiteName: "group.daniesy.text")!            
  defaults.addObserver(self, forKeyPath: "temp", options: NSKeyValueObservingOptions.New, context: nil)
  defaults.setBool(!defaults.boolForKey("temp"), forKey: "temp")
  defaults.synchronize()
  
  override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer&lt;Void&gt;) {
      println("changed")
  }
  </code></pre>
  
  <p>However if i ignore the appGroup and use <code>NSUserDefaults.standardUserDefaults()</code> it works as expected.
  Any idea why it's not working?</p>