changelog update

Author: Ioannis Giagkiozis

CHANGELOG.md

@@ -5,7 +5,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
-## [0.4.0] - 2020-02-26
+## [0.4.0] - 2020-02-27
 ### Added
 - Documentation for `Plot`
 - A feature (`orca`) that enables `Plot` conversion to the following output formats: png, jpeg, webp, svg, pdf and eps