Add note about httpbis to the roadmap
Add note about httpbis to the roadmap

CrankWheel/cowboy,yangchengjian/cowboy,sile/cowboy,bobos/ecweb,callsign-core/cowboy_hybi00,noname007/cowboy,imdeps/cowboy,K2InformaticsGmbH/cowboy,binarin/cowboy,odo/cowboy,Reimerei/cowboy,nviennot/cowboy,bsmr-erlang/cowboy,kivra/cowboy,yangchengjian/cowboy,pap/cowboy,paulperegud/cowboy,acrispin/cowboy,hairyhum/cowboy,binarin/cowboy,grahamrhay/cowboy,ninenines/cowboy,cad627/cowboy,cad627/cowboy,omusico/cowboy,276361270/cowboy,dangjun625/cowboy,rabbitmq/cowboy,callsign-core/cowboy_hybi00,turtleDeng/cowboy