[WIP] Add a test that setuptools can be installed in a clean environment

Restrict use of os.makedirs to those with the security patch introduced in Python 3.2.6, 3.3.5, and 3.4.1 per https://bugs.python.org/issue21082. Ref #1082.

fixed #1042 -- updates an import to use six from the vendored package

Document -s to run single test

Fixes https://github.com/pypa/setuptools/issues/1032

Tox doc comments

This will help get new contributors started, if they're just used to
running "tox".