Move test data to separate package.

[sdgathman]

The deactivated pieces of real viruses in the test data cause virus scanners to alarm. Using the standard test "virus" does not work for this application because we are scanning for disguised executable content - not signatures of known viruses.

By moving the test emails to its own package,

1. scanners will no longer alarm on milter code itself
2. the test emails can be useful in testing other milter applications.

[sdgathman]

The test cases for pymilter are now stored in an encrypted zip. The same technique will work here.