Better support for window

- Properly split %PATH%
- Assume an implied .exe extension
Using double colons for the last three examples

This way it renders OK on pypi.

Note: if you rename the file to `README.rst` you'll get it nicely rendered in github, too.
Add Result.__nonzero__, reflecting the exit status
Add PUN presentation
PUN-inspired documentation additions
Add some missing tests
Version 2.2
Merge tag '2.2' into debian
New debian package