Draft API methods need to be exposed

[Tulon]

I'd like to make use of ZMQ_CLIENT / ZMQ_SERVER socket types with cppzmq, but unfortunately I am not able to, as cppzmq doesn't expose zmq_msg_routing_id() / zmq_msg_set_routing_id(). I can't simply call those functions directly, as zmq::message_t doesn't expose the underlying zmq_msg_t type.

[kurdybacha]

client/server socket are not fully supported yet. client/server message types have been added recently for simple scenario only where there is no need for routing id. It would be great if you could provide a pull request for that.