reenabled gpg_verify test fixture
no message
removed unused import
 - renamed some things in Exportable so they work properly for subclasses
 - tightened up crc24's loop slightly
#93 for SubPacket Header typeid; CreationTime, Issuer length
misc fixes/comment updates
 - implemented a real regression test for #56
 - deleted bug_56.py
 - renamed test_3_actions to test_4_actions
 - added stub for test_3_armor
 - added more to need.txt