title: onHover Button cut out a triangle and show Background
body: <p>I want to cut out a triangle shape if a Button is hover like in this picture:</p>
  
  <p><img src="https://i.stack.imgur.com/u5dUU.png" alt="enter image description here"></p>
  
  <p>I use for my site bootstrap so here is a example for my navbar:
  <a href="http://www.bootply.com/oJeavrQoH6" rel="nofollow noreferrer">http://www.bootply.com/oJeavrQoH6</a></p>
  
  <p>I hope you all understand what I want to do.</p>