title: Autolayout height equal to MAX(multiple view heights)
body: <p>Say I have a view called <code>container</code>. <code>container</code> contains 5 <code>UIButtons</code>. I want to add a height <code>NSLayoutConstraint</code> on <code>container</code>, and this height should be equal to the <code>NSLayoutHeightAttribute</code> of the tallest button in its subviews.</p>
  
  <p>I don't see a straightforward way to do this. Anyone have any ideas?</p>