title: Set height constraint for UITextView
body: <p>I'm fairly new to iOS development and am having a hard time sizing a UITextView to it's content. I've found several examples of calculating a strings render size and/or updating the frame size of a textview, however I can't seem to get those to work. </p>
  
  <p>When I add a UITextView to my view it adds a Height constraint which I think is locking it to a specific height. How can I work around it, update the constraint via code, and/or get my UITextView to resize vertically to show my content?</p>