Merge pull request #664 from hintjens/master

Fixes #663
adding zsock_pollin
changing zsock_pollin to zsock_waiting
Merge pull request #665 from taotetek/master

Problem: creating pollers in language bindings for CZMQ is difficult
adding zsock_ready to compliment zsock_waiting
Merge pull request #666 from taotetek/master

Problem: we can easily check for POLLIN on a zsock but not POLLOUT
Cleaned-up and fixed zsock_ready/waiting code

- proper indentation and hyphens for header
- zsock_ready() was testing ZMQ_POLLIN