Cleaned-up and fixed zsock_ready/waiting code

- proper indentation and hyphens for header
- zsock_ready() was testing ZMQ_POLLIN
Problem: zsock_waiting code is too complex

Solution: just test zsock_event()

In fact these two methods could probably be removed without harm.
Merge pull request #668 from hintjens/master

Cleaned-up and fixed zsock_ready/waiting code