adjust factories and create pending specs for @policy.new_version method
create/refactor tests for policy.needs_new_version?

needs_new_version? will check the dirty object in a before_update callback to see if the policy has changed or just the rule. (I hope)
implement simple #needs_new_version?
add default scope to versions to order by created_at
add tests for policy updates and versioning
add tests and callbacks for updating versions when policy is updated