If you're shipping prerelease or rc packages using Munki, you'll
eventually discover that Munki's version comparison logic is not as
good as pip's. In theory we should be able to fix Munki, but it seems
entirely reasonable to produce version strings that sort reasonably
under these conditions. Since the requried logic not brief, add a new
script and some tests of that logic.
A followup change will wire this into the Makefile.
