title: How to make UILabel resize to fit text
body: <p>I have a UILabel that I have layed out in a storyboard centred in the view. It has some initial text "tap to login".</p>
  
  <p>I am changing the value of the label to be the user's name once they have logged in. Once I do this, the label is no longer centered as the UILabel has not changed size.</p>
  
  <p>How can I do this with autolayout in interface builder?</p>