Add a changelog (#30)

Signed-off-by: Dustin Ingram <di@users.noreply.github.com>

CHANGELOG.md

@@ -0,0 +1,66 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+### Added
+- Add helpful text to README ([#23])
+- Add link to email in README ([#27])
+
+### Fixed
+- Fix small bug with extensions ([#25])
+
+## [0.2.4] - 2019-06-07
+### Fixed
+- Fix typo in extensions ([#21])
+
+## [0.2.3] - 2019-04-20
+### Changed
+- Update sample scripts ([#15])
+
+### Fixed
+- Move Sphinx dependency out of package depedency ([#17])
+
+## [0.2.2] - 2019-01-16
+### Added
+- Adding web app tests ([#13])
+
+### Fixed
+- Add content-type for long-description. ([#11])
+
+## [0.2.1] - 2019-01-16
+### Changed
+- Consolidating return types ([#7])
+- Updates for binary encoding ([#9])
+- 0.2 force improvements ([#10])
+
+## [0.2.0] - 2018-12-08
+### Changed
+- Make SDK compliant wtih CloudEvents SDK spec ([#2])
+
+## [0.0.1] - 2018-11-19
+### Added
+- Initial release
+
+[Unreleased]: https://github.com/cloudevents/sdk-python/compare/0.2.4...HEAD
+[0.2.4]: https://github.com/cloudevents/sdk-python/compare/0.2.3...0.2.4
+[0.2.3]: https://github.com/cloudevents/sdk-python/compare/0.2.2...0.2.3
+[0.2.2]: https://github.com/cloudevents/sdk-python/compare/0.2.1...0.2.2
+[0.2.1]: https://github.com/cloudevents/sdk-python/compare/0.2.0...0.2.1
+[0.2.0]: https://github.com/cloudevents/sdk-python/compare/0.0.1...0.2.0
+[0.0.1]: https://github.com/cloudevents/sdk-python/releases/tag/0.0.1
+
+[#2]: https://github.com/cloudevents/sdk-python/pull/2
+[#7]: https://github.com/cloudevents/sdk-python/pull/7
+[#9]: https://github.com/cloudevents/sdk-python/pull/9
+[#10]: https://github.com/cloudevents/sdk-python/pull/10
+[#11]: https://github.com/cloudevents/sdk-python/pull/11
+[#13]: https://github.com/cloudevents/sdk-python/pull/13
+[#15]: https://github.com/cloudevents/sdk-python/pull/15
+[#17]: https://github.com/cloudevents/sdk-python/pull/17
+[#21]: https://github.com/cloudevents/sdk-python/pull/21
+[#23]: https://github.com/cloudevents/sdk-python/pull/23
+[#25]: https://github.com/cloudevents/sdk-python/pull/25
+[#27]: https://github.com/cloudevents/sdk-python/pull/27