Fix for auto_chmod behavior

Apparently, in (at least) python 3.5.2, the function that is called on Windows to remove files is os.unlink and not os.remove. This results in permission errors when trying to clean up after easy_install has been used to install a package from a Git repository.

Add a test capturing new proposed expectation that Setuptools' build dependencies should not require setuptools to build in order to avoid inevitable conflicts when bootstrapping from source. Packaging fails this test. Ref #980

Python 3.6 invalid escape sequence deprecation fixes

In upload, infer the username using getpass.getuser()

If m is non-true, then has_mfs must have been False.

A local version label starts with a '+' sign

support dist-info distributions inside zip files

Dropped support for classifiers subsection handling in setup.cfg

 Fix hard link to URLs that should have been internal (method 2: via autosectionlabel Sphinx extension)

Add --skip-dep-install to boostrap.py script

The --skip-dep-install flag skips installation of setuptools dependencies
using pip, delegating this responsibility to other tools.  This can be used to
install setuptools without the need for pip.

closes #950