title: UIManagedDocument proper initialization and wait until it is ready
body: <p>I'm trying to use CoreData with an <code>UIManagedDocument</code> and I know it takes a little while until it is ready to go, and I also know that it fires a notification when it's ready. I want to display the app when its ready, is it convenient to do it this way?</p>
  
  <p>What would be the standard approach (time and way) for initializing a <code>UIManagedDocument</code> and waiting until it's ready to go?</p>
  
  <p>What happens with applications that show data from the very start?</p>