Update CHANGELOG to match 0.6.0.

Author: kw217

CHANGELOG.md

@@ -7,11 +7,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 ### Added
 
+### Changed
+
+## [0.6.0] - 2017-09-25
 ### Changed
 - Authorization struct now has new field `issuer`.
 
 ## [0.5.0] - 2017-09-18
 - Start of changelog.
 
 [Unreleased]: https://github.com/Metaswitch/swagger-rs/compare/0.5.0...HEAD
+[0.6.0]: https://github.com/Metaswitch/swagger-rs/compare/0.5.0...0.6.0
 [0.5.0]: https://github.com/Metaswitch/swagger-rs/compare/0.4.0...0.5.0