[ietf-dkim] Issue 1561: Development & Deployment guide improperly uses normative language

[Stephen Farrell]

Issue description: https://rt.psg.com/Ticket/Display.html?id=1561

Thread: http://mipassoc.org/pipermail/ietf-dkim/2008q1/009790.html

 From the thread people seem to support the thrust of the comment, i.e.
to reduce/eliminate 2119 language where possible and definitely
avoid it (regardless of case) where its not needed.

Suggest we leave this open for now to let the editors concentrate
on the overview and process the deployment draft issue subsequently.

S.