Socket Factory: Use SOCKOPT_LINGER by default.
Socket Factory: Use SOCKOPT_LINGER by default.

By setting ZMQ::SOCKOPT_LINGER to 0, the sockets will be destroyed even
when there are still messages to be sent.

Fixes #15.

Signed-off-by: Jacob Kiers <f862f167b85d41b225785c70d70808bc7337c1fe@alphacomm.nl>

alphacomm/alpharpc,alphacomm/alpharpc