Update changelog

Author: mblaschke

CHANGELOG.md

@@ -2,6 +2,10 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [WebDevOps.io Dockerfile](https://github.com/webdevops/Dockerfile).
 
+## [0.21.6] - 2016-03-25
+### Changed
+- Refactored directory layout (container -> docker/, .bin -> bin, testsuite -> test/
+
 ## [0.21.5] - 2016-03-24
 ### Added
 - Fixed permissions automatically for /tmp if mounted as volume