Remove Python dependency from swc-windows-installer.py

We currently have an installer that handles the issue of installing `nano` into msysgit for use with Git: https://github.com/swcarpentry/bc/blob/master/setup/swc-windows-installer.py.

This currently doesn't help for bootcamps where Python is not installed, so it would be handy to have a version of this that doesn't rely on a Python install.  I see two paths forward:
 
@ethanwhite says:
> If someone is looking for a short project at
some point pulling this script into it's own directory, adding a
setup.py file, and packaging it using py2exe that would be a nice
contribution to making things even easier on Windows.

Another option would be to reimplement the script's functionality in R.  Please put a hand up if you're interested in taking this on.