Bump version to v0.2.1.

CHANGELOG.md

@@ -9,6 +9,12 @@ The format is based on [Keep a Changelog], and this project adheres to
 [Keep a Changelog]: https://keepachangelog.com/en/1.0.0/
 [Semantic Versioning]: https://semver.org/spec/v2.0.0.html
 
+## [0.2.1] - 2020-03-17
+
+## Fixed
+
+- Prevent `backoff.Exponential()` and `Linear()` from overflowing `time.Duration`
+
 ## [0.2.0] - 2020-03-06
 
 ## Added
@@ -35,6 +41,7 @@ The format is based on [Keep a Changelog], and this project adheres to
 [0.1.0]: https://github.com/dogmatiq/linger/releases/tag/v0.1.0
 [0.1.1]: https://github.com/dogmatiq/linger/releases/tag/v0.1.1
 [0.2.0]: https://github.com/dogmatiq/linger/releases/tag/v0.2.0
+[0.2.1]: https://github.com/dogmatiq/linger/releases/tag/v0.2.1
 
 <!-- version template
 ## [0.0.1] - YYYY-MM-DD