When setting headers the header value must not include linebreak charachters

[CrowdHailer]

Raxx.set_header(message, key, value) must not accept a value containing the \r or \n charachters.

https://github.com/elixir-plug/plug/blob/master/lib/plug/conn.ex#L1269-L1274

QUESTION: should the header key not be checked to ensure no newline charachters. I guess also no colon (:)

Docs for set header should reference rfc7540 for acceptable charachters in header and value

[CrowdHailer]

Fixed in PR #96