Eliminate usage of use_mailbox
add DealerSocket and RouterSocket
Merge pull request #17 from grantr/extra_sockets

add DealerSocket and RouterSocket
depend on ffi-rzmq with fixed socket monitoring
add PairSocket
add read_message to ReadableSocket

Reads raw ZMQ::Message objects off the socket. This is needed
to read from monitoring sockets.
add a Socket#monitor method

Sets up an internal pair socket that publishes socket events to an
inproc endpoint. Another pair socket can be connected to the endpoint to
read those events.

Only works with ZeroMQ 3.2+ and ffi-rzmq > 0.9.7. The method is not
defined for earlier versions of ffi-rzmq because it doesn't have the
necessary constants.

See http://api.zeromq.org/3-2:zmq-socket-monitor for more info.
add socket monitor actor

Starts up a pair socket connected to the monitoring endpoint. Override
dispatch to handle socket events.
require socket_monitor at the end

It needs to be required after zmq.rb does its thing
fix typo
use the correct constant
use Celluloid::Logger to log