Changes since 0.4.0:
* Man pages for pyzor and pyzord.
* Changing back to signals for database locking, rather than threads.
It is likely that signals will be removed again in the future, but
the existing threading changes caused problems.
* Basic checks on the results of "discover".
* Extended mbox support throughout the library.
* Better handling on unknown encodings.
* Added a --log option to log to a file.
* Better handling of command-line options.
* Improved error handling.
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