rack/rack — pull request #404 by pje (2012-07-09 11:02:32+00:00)
Title: Add new status codes to `Rack::Utils.HTTP_STATUS_CODES`

From [RFC 6585](http://tools.ietf.org/html/rfc6585):

- 428 [Precondition Required](http://tools.ietf.org/html/rfc6585#section-3)
- 429 [Too Many Requests](http://tools.ietf.org/html/rfc6585#section-4)
- 431 [Request Header Fields Too Large](http://tools.ietf.org/html/rfc6585#section-5)
- 511 [Network Authentication Required](http://tools.ietf.org/html/rfc6585#section-6)