Simple encryption service Goodie

This is a simple encryption service as requested at https://duck.co/ideas/idea/1463/simple-encryption-service

# ABSTRACT: This goddie provides a simple encription/decryption service
# using RC4 algorithm and a key provided by the user.
# Usage: crypto encrypt key text
#        crypto decrypt key text
# or the short form
#        crypto en key text
#        crypto de key text