Support Python 2.6, 2.7, 3.3, 3.4, and pypy.

Add testenvs to tox.ini for these configs.

Adds a dev dependency on unittest2 for python 2.6.
Adds a dependency on ordereddict for python 2.6.
__metaclass__ doesn't actually set the metaclass in py3k, and the new syntax, class Foo(bases, metaclass=meta), is a syntax error in python 2.

So we actually create the class not with the class keyword, but by making a call directly to SomeMeta (and in turn wrapping that with genty). Metaclass __init__ has the signature (name, bases, attrs), so we pass the name SomeParent, a tuple containing object for the base class, and the test_parent method we want the class to have.