ENH: Easy version parsing

Ready for review/merge @drammock or @rkmaddox. Realized it's nice to have this to know which version is currently checked out when finalizing an experiment.
Sorry, I mean if it is an empty list. Sometimes I do not wish to stamp, but a ttl_id argument is required. In this case I pass an empty list. This used to stamp [8, 8] anyway. Now it won't stamp anything, which is good, but there's no reason to even call the function.