Move fuubar to development dependencies.
Use kankri for authentication.

kankri is just a spin-off of bra's authentication system, so this should work
perfectly.
Forgot Gemfile.lock.
Fix bug when post_forwarding to Constants.

A Poster will now only default to trying to change to a PUT if the object can
have children (this excludes Constants).
Use kankri exceptions.

Also fix a stream bug whereby the privilege set was discarded entirely.