ZyreEvent: use properties. Create string rather than CData
ZyreNode: Implement recv_event. Recieve zyre_events
ZyreEvent: __repr__ and __str__
ZyreEvent: Handle null pointers in zyre_event_* return values.
ZyreEvent: Added event type
ZyreEvent: Added header.
Added c_string_to_py. Utility lambda to convert c string to python string which supports null pointers which will be None.
ZyreEvent: Use c_string_to_py
ZyreEvent: Add msg_string, wrapper for zyre_event_msg