ISSUE-108: Do progress total/loaded measure body content only, or include respose headers etc.?

ISSUE-108: Do progress total/loaded measure body content only, or include respose headers etc.?

http://www.w3.org/2005/06/tracker/webapi/issues/108

Raised by: Charles Mccathienevile
On product: Progress Event

I think the sense of the group is that we don't include the transaction 
headers. I wonder if that is the right decision though.