Provide script to show off integration with btar

[nanch]

btar looks like a very interesting piece of software. it could be used to provide the best features to users looking for advanced feature sets.

Philosophically, tarbackup is focused on using simple existing tools that have been well-proven in the field, but it would be nice to provide a recommendation for the best client-side archiving tool. The go-to is tar or duplicity, but btar looks interesting too.