title: Implement getHeadRotation android panoramic view
body: <p>I want to get the yaw and pitch of the head just like in the method nativeGetHeadRotation given in class VrPanoramaRenderer of the GVr sdk. I have not been able to just use this method without actually using the VRPanoramaView itself. I create my custom renderer that I attach to a GLSurface, but on every drawFrame I want to check how much the head has moved by and render something. </p>
  
  <ol>
  <li>How do I go about implementing getHeadRotation? </li>
  <li>Should I just follow the getRotationMatrix approach and use the yaw and pitch from that?</li>
  </ol>