adjust RawHeaderLine to be (String, Vec<u8>)
Merge pull request #72 from hyperium/header-name-string

adjust RawHeaderLine to be (String, Vec<u8>)
Basic Cookie and Set-Cookie (only parsing) headers implementation.
Add cookie-rs and use `cookie::Cookie` in `Cookie` header.
Build SetCookie from CookieJar
Add cookie_rs as default feature and implement conditional compilation.