Use new-style classes

Use python's new-style classes (inherit explicitly from 'object').  When I inherit from AuthorizationProvider, I'd expect to use the new super() syntax, super(MyAuthorizationProvider, self).__init__(), rather than the old-style AuthorizationProvider.__init__().  I know that AuthorizationProvider doesn't currently have an __init__() method, but if it adds one someday, I'll want to be sure that my subclass called it.

The difference between old- and new- style classes is described here: http://docs.python.org/2/reference/datamodel.html#new-style-and-classic-classes

Old-style classes are going away in python 3, so we might as well hop on board.