title: Animate opening a new window with NSWindowController
body: <p>Starting with Mac OS X 10.7, new <code>NSDocument</code> windows as well as alert windows open with an animation. Windows opened with <code>NSWindowController</code>'s <code>showWindow:</code> method, however, get no animation.</p>
  
  <p>Is there a way for these windows to get the same animation?</p>