Add 0.5.2 release notes

Cherry-pick of 4a780d0 and 0466286

CHANGELOG.md

@@ -4,20 +4,31 @@ The format is based on [Keep a Changelog][], and this project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 [Keep a Changelog]: https://keepachangelog.com/en/1.0.0/
-[Unreleased]: https://github.com/yourbase/yb/compare/v0.5.1...HEAD
+[Unreleased]: https://github.com/yourbase/yb/compare/v0.5.2...HEAD
 
-## [0.5.1][] - 2020-11-18
+## [Unreleased][]
+
+### Fixed
+
+-  The Ruby buildpack downloads a pinned version of rbenv and ruby-build rather
+   than following the latest commit.
+
+## [0.5.2][] - 2020-11-18
 
-Version 0.5.1 fixes a major regression in `yb build` behavior.
+Version 0.5.2 fixes a major regression in `yb build` behavior.
 
-[0.5.1]: https://github.com/yourbase/yb/releases/tag/v0.5.1
+[0.5.2]: https://github.com/yourbase/yb/releases/tag/v0.5.2
 
 ### Fixed
 
 -  Regression: `yb build` would exit with a zero status code on build failures
    in version 0.5. This is now fixed.
--  The Ruby buildpack downloads a pinned version of rbenv and ruby-build rather
-   than following the latest commit.
+
+## [0.5.1][] - 2020-11-18
+
+Version 0.5.1 was a botched release.
+
+[0.5.2]: https://github.com/yourbase/yb/releases/tag/v0.5.1
 
 ## [0.5.0][] - 2020-11-18