Merge pull request #659 from hintjens/master

Fixed Z85 methods to be static
Merge pull request #660 from hintjens/master

Added z85 codec to ZMQ API
simplify test_security_curve.cpp with zmq_z85_encode
Merge pull request #661 from lalebarde/master

simplify test_security_curve.cpp with zmq_z85_encode
Fix windows build
Merge pull request #662 from ricnewton/master

Fix windows build
Fixed random failures in test_security_plain and _curve

* ZAP handler thread was not getting time to start up
* Code now creates and binds handler socket in parent thread and
  passes the socket to the zap_handler, so this always gets the
  authentication requests.