HTTP/2 Draft 16

Motivation:
HTTP/2 draft 16 has been released https://tools.ietf.org/html/draft-ietf-httpbis-http2-16.

Modifications:
The HTTP/2 codec should be updated to support draft 16.

Result:
HTTP/2 codec is draft 16 compliant.
Hmm ... we still have 3 open methods.  Could we just get rid of the open(boolean) version and leave openForPush() and open()?  I don't think the interface needs all 3.