Merge pull request #591 from hurtonm/master

Rename parse_properties to parse_metadata
Store identity for raw socket

Identity stored during connect procedure. Can be read using
zmq_getsockopt and used as the identity frame when sending messages.
This allows the implementation of a raw socket client.
Merge pull request #592 from gavinmcniff/master

Store identity for raw socket
Added ZMQ_STREAM socket type

- designed for TCP clients and servers
- added HTTP client / server example in tests/test_stream.cpp
- same as ZMQ_ROUTER + ZMQ_ROUTER_RAW + ZMQ_ROUTER_MANDATORY
- includes b893ce set ZMQ_IDENTITY on outgoing connect
- deprecates ZMQ_ROUTER_RAW
Merge pull request #593 from hintjens/master

Problem: ROUTER+RAW was not a clean API
Simplify STREAM socket implementation