update changelog

Author: jfromaniello

CHANGELOG.md

@@ -4,6 +4,10 @@
 All notable changes to this project will be documented in this file starting from version **v4.0.0**.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## 7.1.0 - 2016-07-12
+
+ - Exp calculated based on iat. fix #217 ([757a16e0e35ad19f9e456820f55d5d9f3fc76aee](https://github.com/auth0/node-jsonwebtoken/commit/757a16e0e35ad19f9e456820f55d5d9f3fc76aee)), closes [#217](https://github.com/auth0/node-jsonwebtoken/issues/217)
+
 ## 7.0.0 - 2016-05-19
 
  - change jwt.sign to return errors on callback instead of throwing errors ([1e46c5a42aa3dab8478efa4081d8f8f5c5485d56](https://github.com/auth0/node-jsonwebtoken/commit/1e46c5a42aa3dab8478efa4081d8f8f5c5485d56))