added autoscripts magic, including related cmd line optioo -n/--noscripts
added actual postinst code to update the Python interpreter
changelog entry for postinst autoscript, and bumping version for requiring this in Build-Depends
Merge pull request #61 from jhermann/trigger-on-python-update

Mirror any host Python interpreter update (closes #48)

Huge thanks to @jhermann for making this change!