Support Python 3.3.0 for extension suffix

Use packaging.version.Version to sort filenames by the version of the package they represent. Alternate implementation of that proposed in #829. Also ref #629.

Add test to verify the install of Pypi top packages

In setuptools 27.0+ extension building fails on Python 3.3.0 because the extension suffix is obtained using `SO` and not `EXT_SUFFIX` (which is used in 3.3.1 and above). See: https://hg.python.org/cpython/file/v3.3.0/Lib/distutils/command/build_ext.py#l673

This patch tries `EXT_SUFFIX` and falls back to `SO` if `EXT_SUFFIX` is falsey.

Add a namespace module.

Remove _add_defaults_data_files override

Fix spacing after comment hash.

Fix quantity of blank lines.

Fix spacing after comment hash.