Add ArgumentParser class

CLI class was modified to support arguments and options.
Add empty args to test to prevent false red tests

If no arguments are provided with the :args option, CLI sets the
unparsed_args variable to ARGV. This is fine if you invoke rspec without
any flags, but if you do something like "rspec --format=doc" then the
application will throw an "invalid option" error during some tests (due
to rspec having a different set of flags than this application).

This change ensures the args are empty.