[Distutils] Expectations on how pip needs to change for Python 3.4

[Daniel Holth]

It is easy to forget that pip only needs the "package database" part
of setuptools (pkg_resources.py) to install things. With the small
catch that the rest of setuptools is required to install anything
besides wheels.

MEBS is just about implementing build requirements properly and giving
pip a consistent interface to build traditional sdists *or* any new
(sdist 2.0, distil, bento) kinds of packages that may come along.