Preparing release v 1.6.0 (#66)

This releases v1.6.0.

CHANGELOG.md

@@ -4,7 +4,7 @@ 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]
+## [1.6.0] - 2020-02-24
 ### Changed
 - Drop library dependency on `golang.org/x/{lint, tools}`.
 
@@ -52,7 +52,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Initial release.
 
-[Unreleased]: https://github.com/uber-go/atomic/compare/v1.5.1...HEAD
+[1.6.0]: https://github.com/uber-go/atomic/compare/v1.5.1...v1.6.0
 [1.5.1]: https://github.com/uber-go/atomic/compare/v1.5.0...v1.5.1
 [1.5.0]: https://github.com/uber-go/atomic/compare/v1.4.0...v1.5.0
 [1.4.0]: https://github.com/uber-go/atomic/compare/v1.3.2...v1.4.0