Update changelog for release

Author: amckenzie

CHANGELOG.md

@@ -4,6 +4,8 @@ on [Keep a CHANGELOG](http://keepachangelog.com/). This project adheres to
 [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
+
+## [6.1.0] - 2018-09-28
 ### Changed
 - All SystemCommandHandler methods now also take a mandatory commandId as a parameter
 - SystemCommander JMX bean now returns a unique command id for each command that it runs