Merge pull request #668 from hintjens/master

Cleaned-up and fixed zsock_ready/waiting code
removing zsock_pollin and zsock_pollout
Merge pull request #669 from taotetek/master

Problem: new methods added complexity with no functionality gain
zpubsub implemented, with examples and doc
Added zpubsub_option class; using options in zpubsub.
Merge branch 'zpubsub'

Finished work on the zpubsub class, with corresponding zpubsub_option
static companion class.
Added check for broadcast interface in zpubsub_test, skipping system test
if no broadcast interface is available.
Merge pull request #670 from lovmoen/master

zpubsub class
Fix forcing into to bool warning.
Add missing exports to zgossip.
Make implicit casts explicit (fixes MSVC errors).
Update NuGet package.
zdir: use S_ISDIR macro instead of masking yourself
Bring back zring_node_t
Add ztimeout class
Merge pull request #672 from Q-Leap-Networks/pull-zdir-isdir

zdir: use S_ISDIR macro instead of masking yourself
Problem: Can't install due to missing czmq.7

Solution: Changing name part in docs/czmq.txt from CZMQ back to czmq.
Currently asciidoc thinks that man page should be named CZMQ.7 and
installer searches for czmq.7. Options are either rename the man page
back or change makefile to expect CZMQ.7. Personally I would expect
lowercase names for man page (and it is referenced like that several
times), so changing to lowercase.
Merge pull request #671 from evoskuil/master

Fix MSVC build breaks and update NuGet package.
Merge pull request #673 from Q-Leap-Networks/pull-ztimeout

Pull ztimeout
Merge pull request #674 from miska/master

Problem: Can't install due to missing czmq.7