renamed pgpy.key to pgpy.keys; moved PGPSignature and PGPKey to pgpy.pgp
added PGPKeyCollection to pgpy.__init__.py so it can be used directly from `import pgpy` as `pgpy.PGPKeyCollection`
added new method "is_ascii(self)" to allow a FileLoader object (or subclassed FileLoader object) to determine if its contents are ASCII or not
cleaned up imports slightly
moved PGPDump up to the pgpy package;
added a new static method bytefield to reduce some existing code duplication;
added support for formatting Trust packets
added some more classes to top-level visibility in pgpy.packet for convenience
added support for Trust packets; fixed Subpackets.__getattr__
added a checklist comment to the PGPPacket factory method; added support for Trust packets
renamed ASCII_ARMOR_BLOCK_REG to ASCII_BLOCK
created PGPLoad factory function to instantiate PGPBlock subclasses; added __getattr__ to PGPKey, and gave it logic to properly determine .sec and .keyid
updated unit tests
added more testdata - test loading a pair of keys from an ASCII armored file (for testing PGPLoad)
reflected added support for Trust packets