Add changes for 0.9.0 for History.rdoc

Generated from `git log --oneline v0.8.0..HEAD | grep 'Merge pull request'` then manually edited. cc @mtodd @schaary. Add a date when we decide to release.
Fixed in 9e1af51ade3c371db7b15117d7a977fb563d67aa. Followed convention from earlier release with a "Code clean-up" section