Replace mmozuras/pronto with prontolabs/pronto in CONTRIBUTING

CONTRIBUTING.md

@@ -27,7 +27,7 @@ do so.
 * Open a [pull request][4] that relates to *only* one subject with a clear title
   and description in grammatically correct, complete sentences.
 
-[1]: https://github.com/mmozuras/pronto/issues
+[1]: https://github.com/prontolabs/pronto/issues
 [2]: http://gun.io/blog/how-to-github-fork-branch-and-pull-request
 [3]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
 [4]: https://help.github.com/articles/using-pull-requests