add experimental connection get message buffer method
fix interface mismatch
Server header/User agent adjustments & tests

Updates behavior to drop the headers if user_agent is set to the empty
string and to allow overriding the Server header from the validate
function. Updates docs and adds a number of tests
Merge branch 'master' into permessage-deflate
update changelog
remove debug printing
permessage_deflate tests
remove deprecated constants
update copyright date
Refactors URI to be exception and regex free
temporary workaround for a g++ compile issue
Merge branch 'master' into permessage-deflate

Conflicts:
	examples/scratch_client/SConscript
impliment no_context_takeover options