message: Fix link to the contribution guide in README.md
diff: @@ -105,7 +105,7 @@ This library uses ES6 Promises so be sure to provide a polyfill for it for the b
  You are welcome to contribute to this repo with anything you think is useful. Fixes are more than welcome.
  However if you are adding a new validation rule, it should have multiple uses or be as generic as possible.
  -You can find more information in the [contribution guide](contributing.md).
  +You can find more information in the [contribution guide](CONTRIBUTING.md).
  ### Tutorials and Examples
  