Add status

Add 102, 207, 208, 422, 423, 424, 426, 429, 431, 506, 507, 508, 510 and 511.

Asking a review from @hoaproject/hoackers :-).
Nop, [RFC7231, section 6.6.6.](http://tools.ietf.org/html/rfc7231#section-6.6.6) :smiling_imp:.