Fix links in CONTRIBUTING.md

CONTRIBUTING.md

@@ -8,6 +8,6 @@ Don't go straight to a pull request in case it's something I don't wish to accep
 ## Fixing a bug
 If you've found a bug, please start by [creating an issue][create_issue]. If you'd like to [make a pull request][create_pr] for the fix once I've confirmed it's a bug in Avatar, that would be great.
 
-[create_issue]: ./issues/new
-[create_pr]: ./compare
+[create_issue]: https://github.com/monooso/avatar/issues/new
+[create_pr]: https://github.com/monooso/avatar/compare