Update changelog

Author: John Kelly

CHANGELOG.md

@@ -4,6 +4,11 @@ All Notable changes to `php-amqplib/thumper` will be documented in this file.
 
 Updates should follow the [Keep a CHANGELOG](http://keepachangelog.com/) principles.
 
+## 0.5.0
+
+### Added
+- Ability to change message parameters.  e.g. content_type
+
 ## 0.4.1 - Added Package Maintenance Files
 
 ### Added