nghttpx: Fix bug CONNECT does not work
nghttpx: Fix bug content-length is removed
nghttpx: Fix bug writecb is nullptr for HTTP/1 connection
Allow duplicate settings ID in SETTINGS

If multiple same ID are found, use the last one.
Update doc
Remove NGHTTP2_FLAG_END_FLOW_CONTROL
src: Code cleanup
Strict handling of connection error

Following cases are now treated as connection error of type
PROTOCOL_ERROR.

* Receiving HEADERS from client in reserved (local)
* Receiving PUSH_PROMISE against peer-initiated stream
* Receiving WINDOW_UPDATE against in reserved (local, remote)
Update doc
Add test for WINDOW_UPDATE against reserved
src: Use std::thread
Treat reception of DATA in reserved stream as connection error
Use old C style comment
src: Code cleanup
Set protocol version draft-06
Change the value of END_PUSH_PROMISE flag as per the spec
Implement draft-ietf-httpbis-header-compression-02
Fix bug common header disappear if it is evicted
Update README.rst