cli: adding check to allow empty or non-existant subject strings
cli: adding helptext
cli: adding function to add email address to file
cli: updating validation function
cli: adding function to check if email is in file.
cli: fixing check that ensures all add options are passed
cli: adding function to remove email from list
cli: updating help text
cli: removing index check for add function
cli: making help text default if an invalid command is passed
test: updating demo list file
cli: updating cli help to echo if command is invalid
cli: adding fixme to problem argument check code
cli: removing unused variables
cli: removing unused class