Merge pull request #4 from apache/master

Merge Apache Master
STREAMS-179 | Added new thread pool executor to shutdown streams
STREAMS-179 | Added javdoc comments.
STREAMS-180 | InstagramTypeConverter is now able to properly serialize UserDataItem objects into Activities.
STREAMS-180 | Missing javadoc
STREAMS-180 | Fixing issue where NPE could be thrown if a post has no comments
Merge remote-tracking branch 'upstream/master'