message: add alligators.io to backers.md
diff: @@ -63,17 +63,21 @@ It could be you!
  ### $100
  <a href="http://tighten.co/">
  - <img width="200px" src="http://i.imgur.com/T7fQYLT.png">
  + <img width="240px" src="http://i.imgur.com/T7fQYLT.png">
  </a>
  <a href="http://invoicemachine.com/">
  - <img width="200px" src="http://assets.invoicemachine.com/images/flat_logo.png">
  + <img width="220px" src="http://assets.invoicemachine.com/images/flat_logo.png">
  </a>
  <a href="https://statamic.com/">
  <img width="240px" src="http://i.imgur.com/MRIkKgp.png">
  </a>
  +<a href="https://alligator.io"></a>
  + <img width="240px" src="https://alligator.io/images/alligator-logo.svg">
  +</a>
  +
  ---
  ### $50+
  