title: Center the PopupView? (vaadin)
body: <p>See <a href="http://demo.vaadin.com/sampler/#ui/structure/popup-view" rel="nofollow">http://demo.vaadin.com/sampler/#ui/structure/popup-view</a></p>
  
  <p>I can create a popup as seen in the vaadin sampler but how can I center to the middle of the window? I thought I could do .center() like you can do with a vaadin window.</p>
  
  <p>Any ideas?</p>