Repare broken link to licence (h5bp#462)

Author: billyjov

.github/CONTRIBUTING.md

@@ -67,4 +67,4 @@ Adhering to the following process is the best way to get your work included in t
 7. [Open a Pull Request](https://help.github.com/articles/using-pull-requests/)
     with a clear title and description.
 
-**IMPORTANT**: By submitting patches, you agree to allow the project owners to license your work under the terms of the [MIT License](LICENSE.md).
+**IMPORTANT**: By submitting patches, you agree to allow the project owners to license your work under the terms of the [MIT License](../LICENSE.md).