THRIFT-4571: Updated ZeroMQ examples to ZeroMQ version >= 3.0. (#1556)

* New style for Python is default now.
* Symbols were replaced in newer versions of ZeroMQ (>=3.0).
* Use Thrift's abstraction for `shared_ptr` instead of Boost.
* Symbols were replaced in Python as well.
diff --git a/contrib/zeromq/test-client.py b/contrib/zeromq/test-client.py
index 55c23e0..d51216e 100755
--- a/contrib/zeromq/test-client.py
+++ b/contrib/zeromq/test-client.py
@@ -15,7 +15,7 @@
     if len(args) > 1:
         incr = int(args[1])
         if incr:
-            socktype = zmq.DOWNSTREAM
+            socktype = zmq.PUSH
             endpoint = "tcp://127.0.0.1:9091"
 
     ctx = zmq.Context()