don't use REQ/REP in devices docs
don't use REQ/REP in devices docs

closes #351
Mustard-Systems-Ltd/pyzmq,ArvinPan/pyzmq,ArvinPan/pyzmq,caidongyun/pyzmq,caidongyun/pyzmq,caidongyun/pyzmq,swn1/pyzmq,dash-dash/pyzmq,yyt030/pyzmq,dash-dash/pyzmq,yyt030/pyzmq,ArvinPan/pyzmq,swn1/pyzmq,swn1/pyzmq,dash-dash/pyzmq,Mustard-Systems-Ltd/pyzmq,Mustard-Systems-Ltd/pyzmq,yyt030/pyzmq