CHANGELOG.md update

Author: Ashwin A Nair

CHANGELOG.md

@@ -2,7 +2,7 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## [4.1.2]
+## [4.1.2] - 2020-04-08
 
 ### Changed 
 - [Dependency upgrade for BC, Checkstyle & Codec libraries](https://github.com/joyent/java-http-signature/pull/62)