Updates CHANGELOG.
Bump to 0.7.0
Fixes #2: updated_at-columns not working anymore.
Bump to 0.8.0
Whoa! Removes ruby version from Gemfile.
Bump to 0.9.0
We are still on minitest 4. 😞
Bump to 0.9.1
Urghh. We are still on minitest 4.
Adds both callbacks for undo and redo.
Bump to 0.10.0
Some changes to README.md.
Updates to mongoid 4.0.0.beta1.