The current Dev version of TarSum includes hashing of extended
file attributes and omits inclusion of modified time headers.
I refactored the logic around the version differences to make it
more clear that the difference between versions is in how tar
headers are selected and ordered.
TarSum Version 1 is now declared with the new Dev version continuing
to track it.
Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)