CLI doesn’t recognize string argument correctly

[mathiasbynens]

After installing via npm install morse -g:

$ morse -d '-.-. --- -. --. .-. .- - ..- .-.. .- - ..'
Usage: /usr/local/bin/morse [options] string

Options:
  -d, --decode  Decode a string of Morse code
  -h, --help    Show this text