title: How to rotate a SCNSphere using a pan gesture recognizer
body: <p>I created an SCNSphere so now it looks like a planet kind of. This is exactly what I want. My next goal is to allow users to rotate the sphere using a pan gesture recognizer. They are allowed to rotate it around the X or Y axis. I was just wondering how I can do that. This is what I have so far.</p>
  
  <pre><code>origin = sceneView.frame.origin
  node.geometry = SCNSphere(radius: 1)
  node.geometry?.firstMaterial?.diffuse.contents = UIImage(named: "world.jpg")
  
  let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(CategoryViewController.panGlobe(sender:)))
  sceneView.addGestureRecognizer(panGestureRecognizer)
  
  func panGlobe(sender: UIPanGestureRecognizer) {
      // What should i put inside this method to allow them to rotate the sphere/ball
  }
  </code></pre>