Add wordcount example from spark

Author: Martin Durant

examples/network_wordcount.py

@@ -0,0 +1,24 @@
+#! /usr/env python
+""" a recreation of spark-streaming's network_wordcount
+
+https://spark.apache.org/docs/2.2.0/streaming-programming-guide.html#a-quick-example
+
+Run this within an interactive session, or with
+> python -i -network_wordcount.py
+so that python won't exit before producing output.
+"""
+
+from streamz import Stream
+
+# absolute port on localhost for now
+s = Stream.from_tcp(9999)
+s.map(bytes.split).flatten().frequencies().sink(print)
+
+print(
+    """In another terminal executs
+> nc 127.0.0.1 9999
+and then start typing content
+"""
+)
+
+s.start()