Toying around with different ideas for prompt API. Current winner is to make prompt an option to be used when describing parameters rather than a res api function.
Completely removed prompt from the API for now. I will add it back as a parameter option. Invoke won't even be called until prompts have been resolved.
Reorganized the shell execute function so it is easier to follow and made prompt an option that can be specified in a command's defined options.
Updated tests and README documentation to cover the new changes to prompts and the command module API.