Set release date

Author: gtauriello

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](https://keepachangelog.com/),
 and this project adheres to [Semantic Versioning](https://semver.org/).
 
-## v1.0.0
+## v1.0.0 - 2019-02-05
 ### Added
 - Initial release including decoder and encoder for the
   [MMTF specification 1.0](https://github.com/rcsb/mmtf/blob/v1.0/spec.md).