swc-windows-installer.py: Rename ~/.nanorc to ~/nano.rc
swc-windows-installer.py: Rename ~/.nanorc to ~/nano.rc

The nano FAQ hints that this is the prefered path on MS Windows [1],
and Ethan White confirmed it in testing [2].

[1]: http://www.nano-editor.org/dist/v2.2/faq.html#3.9.1
[2]: https://github.com/swcarpentry/bc/pull/357#issuecomment-37482899

ethanwhite/windows-installer,wking/swc-windows-installer,swcarpentry/windows-installer