don't need that
Port english module
let score borrow a Vec<u8> like everything else
clearer xoring
port mod decrypt to crate
port set 1 challenge 3
port set 1 challenge 4
xor on slices, not vectors

it seems that it’s entirely possible to only have a slice, and not have
access to the underlying vector in order to loan the vector itself. for
example, os::args() returns slices and not vectors. that means we have
to be able to xor on and with slices.
bins to xor encrypt and decrypt
fix name of set 1 challenge 4 test
port set 1 challenge 5
crate Binary, impl to_binary() for [u8]
port hamming distance calculator
show key in hex and ascii
we really need to only operate on bytes, sadly
no, really, bytes for everything
tweak unknown byte ranking
solve set 1 challenge 6

decrypt provided ciphertext by finding repeating xor key
add decrypting repeating xor keys to decrypt_xor
and also use slices to score english