Update CHANGELOG

Author: Stephen Powis

CHANGELOG.md

@@ -2,13 +2,12 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## 2.1.0 (UNRELEASED)
+## 2.1.0 (12/20/2018)
 #### New Features
 - Add support for SASL authentication to Kafka clusters.
 - Consumer details can now be viewed on Clusters.
 - Explicitly expose user login session timeout configuration value in documentation.
 
-
 #### Bug fixes
 - Topics shown on brokers now include "internal" topics.
 - Generated consumer client.id shortened.