Almost complete challenge 17

Complete challenge 16

Complete challenge 15

Complete challenge 14

Complete challenge 13

Fix clippy warnings

Complete challenge 12

Complete challenge 11

Complete challenge 10

Fix pkcs7 edge case

Add license and readme

Fix clippy warnings

Complete challenge 9

Complete challenge 8

Complete challenge 7

Complete challenge 6

Refactor xor and improve plaintext scoring

Complete challenge 5

Complete challenge 4

Complete challenge 3