Implementation for -except

This adds an implementation for an "-except" option, including tests and documentation. It should be sufficient to close the two remaining namespace-sweep tickets on rt.cpan.org.

Also, it improves the x-moo.t test to include a test for Moo roles.

Also, it slightly reformats some of the code samples in the pod to ensure they fit on an 80x24 terminal window when using the perldoc utility.

Yeah, sorry to bundle so many unrelated changes.