makerelease: Update the archive defaults

Signed-off-by: Michael Buesch <m@bues.ch>
makerelease.sh: Don't create plain zip archive

Signed-off-by: Michael Buesch <m@bues.ch>
setup.py: Use README.txt as long_description

Signed-off-by: Michael Buesch <m@bues.ch>
setup.py: Add win postinst script

Signed-off-by: Michael Buesch <m@bues.ch>