Update gem dependencies

Updated all the dependencies to the latest versions available as of e542412

I also took into account the conversations in #7 

I've also merged #17 so as soon as that one is merged into master this one should be up to date.
not sure, but the file has been around for a while:  https://github.com/hammernight/taza/commits/master/lib/taza.rb.backup

I'm guessing a backup that slipped through the cracks.