This is a second rev of the Akka upgrade (earlier merged, but reverted). I made a slight modification which is that I also upgrade Hive to deal with a compatibility issue related to the protocol buffers library.

Author: Anand Avati <avati@redhat.com>
Author: Patrick Wendell <pwendell@gmail.com>

Closes #2752 from pwendell/akka-upgrade and squashes the following commits:

4c7ca3f [Patrick Wendell] Upgrading to new hive->protobuf version
57a2315 [Anand Avati] SPARK-1812: streaming - remove tests which depend on akka.actor.IO
2a551d3 [Anand Avati] SPARK-1812: core - upgrade to akka 2.3.4