Fix doc about NetworkWordCount/JavaNetworkWordCount usage of spark streaming

Usage: NetworkWordCount <master> <hostname> <port>
-->
Usage: NetworkWordCount <hostname> <port>

Usage: JavaNetworkWordCount <master> <hostname> <port>
-->
Usage: JavaNetworkWordCount <hostname> <port>

Author: jmu <jmujmu@gmail.com>

Closes #826 from jmu/master and squashes the following commits:

9fb7980 [jmu] Merge branch 'master' of https://github.com/jmu/spark
b9a6b02 [jmu] Fix doc for NetworkWordCount/JavaNetworkWordCount Usage: NetworkWordCount <master> <hostname> <port> --> Usage: NetworkWordCount <hostname> <port>
SPARK-554.  Add aggregateByKey.
Java and Python aggregateByKey
Fix doc (replace T with V)
Fix line lengths