title: Winjs Flyout in the center of the screen
body: <p>When I click on a button, a Flyout will appear for confirmation on the top of the button I have just clicked on.</p>
  
  <p>I tried this :</p>
  
  <pre><code> flyout.alignment="center" 
  </code></pre>
  
  <p>but the alignment is by the button. I want to show my flyout in the center of my screen. I'm asking if this is possible with <code>Winjs.UI.Flyout</code> </p>