Subject: [Acme] Remove MUST for "type" and "detail" in problem docs

From: Jacob Hoffman-Andrews <[email-masked]>
Date: Fri, 26 Feb 2016 10:12:07 -0800

This change brings our use of problem documents more in line with
I-D.ietf-appsawg-http-problem.

https://github.com/ietf-wg-acme/acme/pull/84