Receiving an http request/response will now return errors like HttpHeaderTooBig, instead of the type being set to that.
Added fr::Socket::status_to_string for converting status values into English strings.
Started work on tests for fr::HttpRequest.
Fixed the final POST data variable containing header data it shouldn't (\r\n\r\n).
Fixed fr::Http::header_exists, and family, not converting things to lowercase first.