Duplicity Tutorial needs an update

Hi

Just used the Duplicity tutorial, there is a depricated command used in it -v4 checked the man duplicity it looks like the new way to do it is --compare-data after some testing this gives a resultat that can be used where -v4 just says everything is fine, and dos not actualy check anny thing.

@benzons I ended up going this route and it works like a charm: https://github.com/zertrin/duplicity-backup