fixes for exchange and gmail

complete rewrite; using imapclient, new hash, sqlite index

fix python 3.5 compatability, import blake2b from pyblake2

34f0a0c try importing blake2b from pyblake2 on ImportErrors

improve mutt profile, add systemd unit, python 3.5 compatability

b162cd5 replace f-strings with .format(), python 3.5 compat, fix #4
07d5ad1 add header caching in mutt config for better performance
bc1f574 fix: replace slash in folder names with a dot
e509c96 update version.sh and parsing in setup.py
a63a7fc add systemd unit files for system service running as user
e7ef5e8 add push command to muttrc to open inbox selection on launch

add more packaging support and docker container

use message constructor and store in new first, move on next run

improved packaging and sample muttrc, changed archive filenames

begin version tagging