Add a changelog and bump version to v0.1.0.

CHANGELOG.md

@@ -0,0 +1,29 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog], and this project adheres to
+[Semantic Versioning].
+
+<!-- references -->
+[Keep a Changelog]: https://keepachangelog.com/en/1.0.0/
+[Semantic Versioning]: https://semver.org/spec/v2.0.0.html
+
+## [0.1.0] - 2020-04-20
+
+- Initial release
+
+<!-- references -->
+[Unreleased]: https://github.com/jmalloc/echo-server
+[0.1.0]: https://github.com/jmalloc/echo-server/releases/v0.1.0
+
+<!-- version template
+## [0.0.1] - YYYY-MM-DD
+
+### Added
+### Changed
+### Deprecated
+### Removed
+### Fixed
+### Security
+-->