Add .gitignore for Python .pyc files and etc
Fix parsing for new thread link HTML in Messages

Thanks Michael L. for emailing me about this!
Add option to specify Thunderbird output format

Thanks Andrew A. for the code!
Add debug flag to limit threads fetched

Thanks Andrew A. for the suggestion!
Randomize sleep duration between thread fetches

Thanks Andrew A. for the suggestion!
Improve handling of encoded characters

I have some weirdly-encoded characters in my messages, so this isn't perfect, but your mileage may vary.
Improve README copy a bit