add MANIFEST.in to MANIFEST.in
add MANIFEST.in to MANIFEST.in

otherwise you cannot create an sdist from an sdist

closes #169

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