title: How to center cards in bootstrap 4?
body: <p>I am using bootstrap 4 alpha 3.<br>
  I want to center the card horizontally in the middle across the page.<br></p>
  
  <p><code>Preview / link:</code> <a href="http://codepen.io/vaibhavsingh97/full/VjRAXW" rel="noreferrer">http://codepen.io/vaibhavsingh97/full/VjRAXW</a></p>
  
  <p>I have tried all the different options listed on the bootstrap 4 example page for cards.</p>
  
  <p>How can I achieve this?</p>