Add new HTTP status codes from RFC 6585

See http://tools.ietf.org/html/rfc6585 for further details.

src/cowboy_http_req.erl

@@ -918,6 +918,9 @@ status(423) -> <<"423 Locked">>;
 status(424) -> <<"424 Failed Dependency">>;
 status(425) -> <<"425 Unordered Collection">>;
 status(426) -> <<"426 Upgrade Required">>;
+status(428) -> <<"428 Precondition Required">>;
+status(429) -> <<"429 Too Many Requests">>;
+status(431) -> <<"431 Request Header Fields Too Large">>;
 status(500) -> <<"500 Internal Server Error">>;
 status(501) -> <<"501 Not Implemented">>;
 status(502) -> <<"502 Bad Gateway">>;
@@ -927,6 +930,7 @@ status(505) -> <<"505 HTTP Version Not Supported">>;
 status(506) -> <<"506 Variant Also Negotiates">>;
 status(507) -> <<"507 Insufficient Storage">>;
 status(510) -> <<"510 Not Extended">>;
+status(511) -> <<"511 Network Authentication Required">>;
 status(B) when is_binary(B) -> B.
 
 -spec header_to_binary(cowboy_http:header()) -> binary().