docs: update contributing link (#233)

Author: stensonb

README.md

@@ -395,7 +395,7 @@ There are some ways you can make this module better:
 
 This repository falls under the IPFS [Code of Conduct](https://github.com/ipfs/community/blob/master/code-of-conduct.md).
 
-[![](https://cdn.rawgit.com/jbenet/contribute-ipfs-gif/master/img/contribute.gif)](https://github.com/ipfs/community/blob/master/contributing.md)
+[![](https://cdn.rawgit.com/jbenet/contribute-ipfs-gif/master/img/contribute.gif)](https://github.com/ipfs/community/blob/master/CONTRIBUTING.md)
 
 ## License