docs: update contributing link (#35)

Author: stensonb

README.md

@@ -83,7 +83,7 @@ Feel free to join in. All welcome. Open an [issue](https://github.com/ipfs/js-da
 
 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