title: What's the programmatic way to make a UIImageView pin to it's superview's top, left, right, bottom, equal width, and equal height?
body: <p>I'm trying to understand how auto layout works programmatically. I know we can assign it in the Interface Builder but I want to learn more about how it works underneath.</p>
  
  <p>If someone could show me the code to make a UIImageView pin it's top, left, right, and bottom alignments (as well as equal width and equal height) that would be great!</p>