RC4 implementation for Crystal
Adapted from ruby/rc4
Usage (after adding to shard.yml):
require "rc4"
key = "your key".to_slice
data = "some data".to_slice
# to encrypt
rc4_enc = RC4.new key
encrypted = rc4_enc.stream data # Slice(UInt8)
# to decrypt
rc4_dec = RC4.new key
decrypted = rc4_dec.stream data
encrypted == decrypted # true