* integrate versioning into AR touch method
* add touch to list of :on events, deprecate touch_with_version
* integrate versioning into AR touch method
Since Rails 5.0, belongs_to_required_by_default has been the official ActiveRecord default.
Add the configuration lines necessary to enable this default in both 5.0 and 5.1.
Add "optional: true" where necessary to fix spec failures caused by this change.
Add version-checking conditionals where necessary.
Update the Changelog appropriately.
The reason some projects have both is so that some spec files can be
run in isolation, without the rails stuff. In practice, I don't find
myself ever doing this. So, the complexity of two files is unnecessary.