Update changelog

Author: johnstevenson

CHANGELOG.md

@@ -1,8 +1,11 @@
 ## [Unreleased]
+
+## [1.0.0] - 2018-03-08
   * Added: PSR3 logging for optional status output
   * Added: Existing ini settings are merged to catch command-line overrides
   * Added: Code, tests and other artefacts to decouple from Composer
   * Break: the following class was renamed:
     - `Composer\XdebugHandler` -> `Composer\XdebugHandler\XdebugHandler`
 
-[Unreleased]: https://github.com/composer/xdebug-handler/compare/d66f0d15cb57...HEAD
+[Unreleased]: https://github.com/composer/xdebug-handler/compare/1.0.0...HEAD
+[1.0.0]: https://github.com/composer/xdebug-handler/compare/d66f0d15cb57...1.0.0