Update packaging

Move old `distribute_setup.py`s to new `ez_setup.py`s. Made `setup.py`s only conditionally import `ez_setup` (can make use of setuptools already in the environment).

Update virtualenv to 1.11 and associated pip/setuptools wheels.

Pip won't install externally hosted packages by default, so Cheroot beta vendored in with --find-links for the moment. Hopefully they will release on PyPI soon (even in beta) and that could be removed.