title: Centering two buttons with Cocoa Auto Layout
body: <p>I have a problem with Cocoa Auto Layout and can't get my head around this problem.
  All I'd like to achieve is to have two buttons always centered in a view as depicted below.</p>
  
  <p><img src="https://i.stack.imgur.com/CD2YQ.png" alt="enter image description here"></p>
  
  <p>I've tried lots of different approaches without any success :( please help me out here.</p>