Update CHANGELOG.md (#76)

Author: f3ath

CHANGELOG.md

@@ -20,5 +20,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [1.0.0] - 2017-10-24
 Initial stable release
 
+[Unreleased]: https://github.com/json-api-php/json-api/compare/1.0.2...HEAD
 [1.0.2]: https://github.com/json-api-php/json-api/compare/1.0.1...1.0.2
 [1.0.1]: https://github.com/json-api-php/json-api/compare/1.0.0...1.0.1