Revision history for Perl extension Algorithm::NaiveBayes.
 - Fixed a runtime error in the Gaussian model - the code died looking
   for a rescale() function, which I had forgotten to import. [Manju Putcha]
 - Added save_state() and restore_state() methods, which will help
   consumers (like AI::Categorizer) avoid a pesky "can't find method"
   error when using a restored model.
0.03  Mon May 17 22:11:00 CDT 2004
 - The double-loop inside the predict() method has been turned
   inside-out, so that the outer loop is now over the new attributes,
   rather than over the different labels in the training set.
 - Some internal changes for making customization easier: moved the
   model-creation code to new internal classes, making it easier to
   write additional classes that handle model creation differently.
 - Moved some of the numerical utility functions to a
   Algorithm::NaiveBayes::Util module.
 - We now use sum() and max() from List::Util rather than implementing
   our own.  The ones in List::Util are considerably faster.
 - Added a copyright and license statement. [Spotted by Alexey Tourbin]
0.02  Fri May 23 13:36:48 CDT 2003
 - The do_purge() method was called during training regardless of
   whether the 'purge' flag was set.  This has been fixed.
0.01  Tue Mar 18 18:45:34 2003
 - original version; created by extracting the NaiveBayes code out of
   AI::Categorizer::Learner::NaiveBayes