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.
I can do this, but it is not totally symmetric with `close()`.  The stream is already assumed to be `activate()` and `addStream()` by the `createStream()` method.  You still want me to make this change?