Mail sanity checker, new edition

This version is ported to python (don't bother checking my code, it isnt pythonic; I take the approach that I learn the standard libraries by practise and let the pythonisms adopt me).

Added feature of checking whether a reply has had enough quoted material trimmed, user-configurable.

I'll start versioning these things if it ever gets bigger than 500 LoC, but till then it's just a useful little trifle.