Added a hacky encryption mode. Duplicated the wrapper and callback functions so they can be modified for encryption mode if needed.

Added a test for the encryption mode

Fixed bugs in library and tests. Now seem to be working

added demonstration of encryption mode to README

Fixed the printout to just update the user on progress (it does still print the final encrypted payload).
Added PKCS#7 padding by default to match the default decryption behaviour.
Changed mode to accept only a string.
I think I have fixed the various nit suggestions but may have missed some (or many tbh)
Actually remembered to push changes (wow incredible right)

forgot to check formatting was ok, have fixed some issues with it. flake8 is not happy with the formatting