Updated changelog

Author: mjsalinger

CHANGELOG.md

@@ -1,5 +1,13 @@
 ## Changelog
 
+### 4.0.0
+* BREAKING: Set server_error Code to 500
+* BREAKING: Remove support for node v4
+* new: Added revoke-handler to revoke access token
+* new: Added implicit grant flow
+* new: Switch from jshint to eslint
+* fix: correct client ID check in refresh_token grant type
+
 ### 3.1.0
 * new: Added package-lock.json
 * new: Extend model object with request context