Mary Marnes's comment 1

The comment is:

"- [-17, section 10.5] Section 11.5, 3rd para:  text uses the phrase
"it can note the Node-ID in the response and use this Node-ID to start
sending requests".  It's not clear whether the use of the Node-ID is a
MAY or a MUST.    [Note: Marc's response to this was that it's an open
issue, but this should be clarified prior to publication]."

- I changed the text to use MUST.
- I also changed the previous paragraph to say that the Resource-ID is
  used as destination instaed of the Node-ID.
- Nit in next section: s/resource ID/Resource-ID/
Merge pull request #185 from petithug/mary-barnes-1

Mary Marnes's comment 1