Update design_prototype_decent.py

linux:~> ./design_prototype_decent.py
Test // | Help | Quit
Welcome to the application
>>> help
Test // | Main
This is how you use this application
>>> main
Test // | Help | Quit
Welcome to the application
>>> quit
Test // | Main
Do you really want to Exit? (y/n)
>>> main
Test // | Help | Quit
Welcome to the application
>>> Bye bye