title: Alert that can work on iOS 7 and iOS 8
body: <p>I'm getting dyld: Symbol not found: _OBJC_CLASS_$_UIAlertAction
  when I'm trying to get this monstrosity to run. </p>
  
  <p>How do I weaklink 8.0 stuff?</p>
  
  <pre><code>var device : UIDevice = UIDevice.currentDevice()!;
  var systemVersion = device.systemVersion;
  var iosVerion : Float = systemVersion.bridgeToObjectiveC().floatValue;
  if(iosVerion &lt; 8.0) {
      let alert = UIAlertView()
      alert.title = "Noop"
      alert.message = "Nothing to verify"
      alert.addButtonWithTitle("Click")
      alert.show()
  } else {
      var alert : UIAlertController? = UIAlertController(title: "Noop", message: "Nothing to verify", preferredStyle: UIAlertControllerStyle.Alert)
      if alert {
          let actionStyle : UIAlertActionStyle? = UIAlertActionStyle.Default;
          var alertAction : UIAlertAction? = UIAlertAction(title: "Click", style: actionStyle!, handler: nil)
          if(alertAction) {
              alert!.addAction(alertAction)
              self.presentViewController(alert, animated: true, completion: nil)
          }
      }
  }
  return;
  </code></pre>
  
  <p>Resolved: UIKit had to be marked Optional rather than Required. Simplified version is now:</p>
  
  <pre><code>var device : UIDevice = UIDevice.currentDevice()!;
  var systemVersion = device.systemVersion;
  var iosVerion : Float = systemVersion.bridgeToObjectiveC().floatValue;
  if(iosVerion &lt; 8.0) {
      let alert = UIAlertView()
      alert.title = "Noop"
      alert.message = "Nothing to verify"
      alert.addButtonWithTitle("Click")
      alert.show()
  } else {
      var alert : UIAlertController = UIAlertController(title: "Noop", message: "Nothing to verify", preferredStyle: UIAlertControllerStyle.Alert)
      alert.addAction(UIAlertAction(title: "Click", style:.Default, handler: nil))
      self.presentViewController(alert, animated: true, completion: nil)
  }
  </code></pre>