The .extend() method for classes no longer requires any arguments. It

had previously required both prototype and static attributes, which

behaved differently from Backbone's version.
It also now takes a third option for Spina options. These are the same

arguments found in the @spina decorator. It's really there for some

unit testing, but can be useful in transitioning some code.

Spina and Review Board unit tests pass.
Tested this in an upcoming change.