title: Center text vertically in a UITextView
body: <p>I want to center the text <em>vertically</em> inside a big <code>UITextView</code> that fills the whole screen - so that when there's little of text, say a couple of words, it is centered by height. 
  It's not a question about centering the text (a property that can be found in IB) but about putting the text <em>vertically</em> right in the middle of <code>UITextView</code> <em>if</em> the text is short, so there are no blank areas in the <code>UITextView</code>.
  Can this be done? Thanks in advance!</p>