Prepare changelog for release

CHANGELOG.md

@@ -6,6 +6,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+
+## [0.4.0] - 2020-02-27
+### Fixed
+- `release` command when there is only `Unreleased` and no compare link was provided
+
 ### Removed
 - `bundle` command
 
@@ -33,7 +38,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - `fmt` command to reformat changelog following the spec
 - `show` command to show a specific version
 
-[Unreleased]: https://github.com/rcmachado/changelog/compare/0.3.0...HEAD
+[Unreleased]: https://github.com/rcmachado/changelog/compare/0.4.0...HEAD
+[0.4.0]: https://github.com/rcmachado/changelog/compare/0.3.0...0.4.0
 [0.3.0]: https://github.com/rcmachado/changelog/compare/0.2.0...0.3.0
 [0.2.0]: https://github.com/rcmachado/changelog/compare/0.1.0...0.2.0
 [0.1.0]: https://github.com/rcmachado/changelog/compare/ae761ff...0.1.0