Changed flashcard format to TOML

Uses https://github.com/BurntSushi/toml to decode TOML files. Obviously needs testing
Updated dev version number
Added end of stack message
The 'q' key will now quit flasher
Implemented end of stack function for cardstack
Implemented end of stack functions

Restart, reshuffle and restart
'l' & 'h' keys will now advance/revert stack
Updated the README
Finalised version number