Merge pull request #43 from petal-labs/docs/changelog-compare-links

docs(changelog): backfill compare links for 0.14-0.16

Author: erikhoward

CHANGELOG.md

@@ -181,7 +181,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Telemetry hooks and retry policies
 - Typed error handling
 
-[Unreleased]: https://github.com/petal-labs/iris/compare/v0.13.0...HEAD
+[Unreleased]: https://github.com/petal-labs/iris/compare/v0.16.0...HEAD
+[0.16.0]: https://github.com/petal-labs/iris/compare/v0.15.0...v0.16.0
+[0.15.0]: https://github.com/petal-labs/iris/compare/v0.14.0...v0.15.0
+[0.14.0]: https://github.com/petal-labs/iris/compare/v0.13.0...v0.14.0
 [0.13.0]: https://github.com/petal-labs/iris/compare/v0.12.0...v0.13.0
 [0.12.0]: https://github.com/petal-labs/iris/compare/v0.11.0...v0.12.0
 [0.11.0]: https://github.com/petal-labs/iris/compare/v0.10.0...v0.11.0