Code cleanups

- please do not use Tabs for indentation (read CLASS style guide)
- moved long list of prime numbers to separate header file for ease
  of reading zhash.c.
Fixed include path for czmq.h
Rewrote zmonitor to use zactor

- renamed existing zmonitor -> zmonitor_v2
- renamed zsock_monitor -> zmonitor
- related cleanups in zauth
Merge pull request #594 from hintjens/master

Rewrote zmonitor -> zactor for CZMQ v3
Update zinterface API

Changed the zinterface API to be only stateful, no longer a mix of
stateful and stateless, as per the discussion of #592.
Merge pull request #595 from ahhentz/zinterface

Update zinterface API