added diff links to changelog

CHANGELOG.md

@@ -13,13 +13,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 * Upgraded phpunit to the latest version and improved its config file
 * Updated to `http-interop/http-middleware#0.5`
 
-## 0.4.0 - 2017-02-05
+## [0.4.0] - 2017-02-05
 
 ### Changed
 
 * Updated to `middlewares/utils#~0.9
 
-## 0.3.0 - 2016-12-26
+## [0.3.0] - 2016-12-26
 
 ### Changed
 
@@ -31,7 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 * New option `retryAfter()`
 
-## 0.2.0 - 2016-11-27
+## [0.2.0] - 2016-11-27
 
 ### Changed
 
@@ -40,3 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## 0.1.0 - 2016-10-08
 
 First version
+
+[0.4.0]: https://github.com/middlewares/shutdown/compare/v0.3.0...v0.4.0
+[0.3.0]: https://github.com/middlewares/shutdown/compare/v0.2.0...v0.3.0
+[0.2.0]: https://github.com/middlewares/shutdown/compare/v0.1.0...v0.2.0