title: Create a button on top of UiTableView
body: <p>I am trying to understand how does Facebook Messenger create a button at the button of the screen which stays on top of the <code>UITableView</code> and follows the scrolling as well?</p>
  
  <p><img src="https://i.stack.imgur.com/6eEQu.jpg" alt="Picture taken from the iTunes Store"></p>
  
  <p>I want to implement the blue button on the bottom right. What should be my approach to achieve something like that?</p>
  
  <p>Any push in the right direction will be highly appreciated.</p>