Log Message:
Update pyzor to 0.5.0.

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.