jam is no longer a macro, so it expects a ref.
Ready for the 0.5.0 release.
Shift the sorting from canon to crab to preserve canon's laziness.
Prove that canon is lazy.
Document the move of the sort-by into crab.
Bump version to 0.6.0-SNAPSHOT now that 0.5.0 is out.
Deref the riff ref once only to avoid the (slim) possibility that the final duration and the loop are calculated based on different states of riff.
Beef up some canon tests.
Nils signify rests in the phrase fn.
Document nils in phrase.