Update zmq.hpp

work in progress...
added monitor_t class
added monitor() method
Update zmq.hpp

corrected monitor_t::on_event_unknown prototype
corrected indentation
work in progress...
syntax & bug fixing
modified monitor_t interface
added possibility to unbind.
added possibility to disconnect.
prevent unused expression result warnings from non-debug ZMQ_ASSERT macro expansion
Merge pull request #20 from taurel/master

Add a disconnect method to the socket_t class
Merge pull request #15 from montoyaedu/master

Added monitor_t class
Merge pull request #17 from grefab/master

Allowing for unbind and disconnect
Merge pull request #18 from Kobolog/master

Prevent -Wunused-value warnings from non-debug ZMQ_ASSERT macro
Fix missing include

Add a missing include for std::string.
Adding ability to check for multipart messages
Changed from static_cast to != to avoid warnings
Adding space between function and args to conform with style
Merge pull request #24 from csteifel/master

Added ability to check for more (multipart)
Changed context_t to use new zmq_ctx_* functions
Merge pull request #25 from csteifel/master

Updated to use new zmq_ctx_* functions to create context
Merge pull request #23 from cjuniet/master

Fix missing include