Refactor - Add docstring + formatting + add require statements
Fix computation when replying to an email without any of our account in
the loop
Update bindings for mu4e-headers-mode
Add a mail-pack/load-mail-pack! function to load the mail pack (in case
of ~/.authinfo.gpg edition for example)
Doc - Improve documentation regarding customization, load mail-pack, and
change the main account routine
Refactor - We let the user choose if multiple accounts, otherwise,
return the only account
Refactor - Keep an internal format for the date