This patch also adds support for understanding super calls.
astroid understands the zero-argument form of super, specific to
Python 3, where the interpreter fills itself the arguments of the call. Also, we
are understanding the 2-argument form of super, both for bounded lookups
(super(X, instance)) as well as for unbounded lookups (super(X, Y)),
having as well support for validating that the object-or-type is a subtype
of the first argument. The unbounded form of super (one argument) is not
understood, since it's useless in practice and should be removed from
Python's specification. Closes issue #89.

DuplicateBasesError is emitted when duplicate bases are found in a class,
InconsistentMroError is raised when the method resolution is determined
to be inconsistent. They share a common class, MroError, which
is a subclass of ResolveError, meaning that this change is backwards compatible.

python setup.py develop now works.