Play 2.3.0 final, scala 2.11.1, drop unused akka version

integrationTests do not pass here
Clean up dependencies so integration tests use 2.11.
Fix issue with cancelling tasks and intermitten NPE.
add comment about jdk6 bug.
Merge pull request #138 from sbt/wip/jsuereth-play23

Port to play 2.3.0 final, scala 2.11.1