Fix broken CONTRIBUTING link
@@ -28,4 +28,4 @@ Want to contribute? Great! First, read [our guidelines for contributors][7].
[4]: https://github.com/google/blockly-android/blob/master/COPYING "Apache open source license, version 2.0"
[5]: https://groups.google.com/forum/#!forum/blockly "Blockly developer forum"
[6]: https://developers.google.com/blockly/registration "Blockly developer registration form"
-[7]: https://github.com/google/blockly-android/blob/master/CONTRIBUTING "Contributor guidelines"
+[7]: https://github.com/google/blockly-android/blob/master/CONTRIBUTING.md "Contributor guidelines"
