title: How to open view controllers in a container view without storyboard
body: <p>I want to open a view controller over an existing view controller via button click without using storyboards. How do I do this? Here is what I mean: </p>
  
  <p>Let's say we have three view controllers I can scroll between: </p>
  
  <p>"zeroVC", "oneVC", and "twoVC"</p>
  
  <p>When I press a button on "twoVC" I want to now scroll between:</p>
  
  <p>"zeroVC", "oneVC", and "threeVC"</p>
  
  <p>I tried looking all through stack overflow but they all use storyboards. </p>