Add nym.py
Refactor code to use the Nym class
Merge branch 'nym_class'
Suppress prints by pyaxo
Append date to the title of the message
Support headers added by the user
Improve validation when starting a session
Handle conflicting config file (from older versions)
Encrypt hSub passphrases
Remove the hSub passphrases file when the only nym is deleted
Add the 'In-Reply-To' header to the reply
Mention haveged and rng-tools to increase entropy