possible change to how nested_attributes interact with has_one relations

Looking for some other opinions on how to possibly change how
nested_attributes work on has_one relations. If you're so inclined,
please join the discussion.

https://rails.lighthouseapp.com/projects/8994/tickets/2852-accepts_nested_attributes_for-creating-new-associated-record-when-one-already-exists

Thanks!
Josh