Adds changelog

Author: coding-chimp

CHANGELOG.md

@@ -0,0 +1,17 @@
+# Change Log
+All notable changes to this project will be documented in this file.
+This project adheres to [Semantic Versioning](http://semver.org/).
+
+## [0.2.0] - 2016-04-29
+### Added
+* Ruby 2.0 compatibility
+* CHANGELOG
+
+### Fixed
+* Typos in README
+
+## 0.1.0 - 2016-03-29
+### Added
+* Methods for all OneSignal resources
+
+[0.2.0]: https://github.com/coding-chimp/onesignal/compare/v0.1.0...v0.2.0