title: Anchor a view at the bottom of a UITableViewController
body: <p>I'm building a view which is a <code>UITableView</code>, however I want to anchor a "Write a comment" <code>UITextField</code> at the bottom of the screen.  You can see an example of this on these screenshots from the "Secret" app - the "Write a comment (anonymously)" and "Post" button are anchored to the bottom of the screen regardless of whether you scroll the tableview items up or down.</p>
  
  <p><img src="https://i.stack.imgur.com/kBJyn.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/wriYs.png" alt="enter image description here"></p>
  
  <p>What's the best way to achieve this?  </p>
  
  <p>Should I be embedding a <code>UITableViewController</code> into a <code>UIViewController</code> with the <code>UIView</code> anchored to the bottom of the screen and the tableview anchored to the top of this view?</p>
  
  <p>Is this some kind of <code>UITableView</code> section footer?</p>
  
  <p>Any advice greatly appreciated.</p>