Merge pull request #203 from gavinmcniff/master

Incorporation of ZMQ_STREAM socket type
Fixed socket options to track latest libzmq master

- Added various missing options
- Only selftest CURVE options if libsodium is available
Using proper test keys for CURVE
Trivial name change
Fixed use of ZMQ_STREAM to work with older libzmq

- defines ZMQ_STREAM if it's not defined
- if older libzmq apps try to use ZMQ_STREAM it will assert in libzmq
Merge pull request #204 from hintjens/master

CZMQ doesn't build with libzmq 3.2.3 stable
Minor cleanup of variable name
Merge pull request #205 from hintjens/master

Minor cleanup of variable name
Did not signal error when trying to send empty message

- zmsg_send () was sending zero frames, which was meaningless
- now returns -1
- added test case for this
Merge pull request #206 from hintjens/master

Problem: zmsg_send() does nothing when given an empty message
Fixed issue #208
Added comment on iteration
Merge pull request #209 from hintjens/master

Fixed issue #208
update Makefile with ztree.o
Added note about tivotisation
Merge pull request #210 from hintjens/master

Added note to clarify policy for embedded apps
Use zmq_strerror to show real error cause
Removed definition of 'inline' for Windows

- see issue #212
- it may be necessary to add this back for some MSVC versions
Merge pull request #211 from hintjens/master

Was not showing ETERM properly
zmsg_load should return NULL if unable to load msg