update JWT spec link. closes #112

Author: jfromaniello

README.md

@@ -1,7 +1,7 @@
 # jsonwebtoken [![Build Status](https://secure.travis-ci.org/auth0/node-jsonwebtoken.png)](http://travis-ci.org/auth0/node-jsonwebtoken)
 
 
-An implementation of [JSON Web Tokens](http://self-issued.info/docs/draft-ietf-oauth-json-web-token.html).
+An implementation of [JSON Web Tokens](https://tools.ietf.org/html/rfc7519).
 
 This was developed against `draft-ietf-oauth-json-web-token-08`. It makes use of [node-jws](https://github.com/brianloveswords/node-jws)