Update CHANGELOG

Author: dpc

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## 0.12.0 - ????-??-??
+## 0.12.0 - 2019-08-05
 
 * Update nix dependency to 0.14.0