Merge pull request #458 from tdas/docs-update

Updated java API docs for streaming, along with very minor changes in the code examples.

Docs updated for:
Scala: StreamingContext, DStream, PairDStreamFunctions
Java: JavaStreamingContext, JavaDStream, JavaPairDStream

Example updated:
JavaQueueStream: Not use deprecated method
ActorWordCount: Use the public interface the right way.
(cherry picked from commit 256a3553c447db0865ea8807a8fdbccb66a97b28)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>