Add ability to atomically swap the callback module for a given code
range. The exact code range must already be registered or an error
tuple is returned.
NOTE: This is needed for migrating from Riak Search to Yokozuna, see basho/yokozuna#20.
Add swap/3 API
Forced pushed fix + test.
I could bikeshed about testing the registration swap independent of running server processes, but your test covers both the swap and the result of swapping.
How do bike sheds even get painted.
Thanks for review.