work in progress to import attached public keys and respond encrypted
work-in-progress for #3, attempting to import included public keys
more troubleshooting #3 -- looks like I've run into a python-gnupg bug
Merge branch 'master' into encrypted_response
Merge branch 'master' into encrypted_response

Conflicts:
	bot.py
refactoring encrypted_response to use new GnuPG class
implemented GnuPG.has_public_key_with_uid (#3)
more refactoring to use new GnuPG class (#3)
bug with importing attached keys
GnuPG class now creates homedir if it doesn't exist
turns out = chars in MIME-encoded email get "quoted-printable", so I had to decode them
removed debug print statement
if there is an encrypted part, and it decrypts successfully, decrypt it before checking for sigs and pubkeys (#3)