title: Auto-Layout [Snapkit] change constraints on rotate
body: <p>I have built an app that uses no interface builder using Snapkit to create my Auto-Layout constraints. Everything looks fine in portrait, however a few screen's need some landscape specific constraints.</p>
  
  <p>I've searched here and Google in general for a quick intro on doing this, but couldn't really find anything that was applicable (everything I found was based on using IB or used size classes instead of orientation - I specifically want landscape, not compact vs regular).</p>
  
  <p>So, all my auto-layout constraints are set up in <code>viewDidLoad</code> at the moment.  No doubt at very least, the ones that will be orientation dependant need moving to some kind of delegate/callback method on UIViewController, but I don't know know what that is...</p>
  
  <ol>
  <li>How do I detect an orientation change in order to change my constraints?</li>
  <li>How do I get the current orientation (so when I first load the view controller I can set the right constraints... Or is the function from my above question always called at least once for each VC on load?)</li>
  <li>Outside of a ViewController, such as custom UIView's, how do I detect the orientation change? Should i send out a custom notification event? I'd rather not have my UIViewController tell every subview it has that orientation has changed.</li>
  </ol>
  
  <p>Thanks for any help :)</p>