=pro,doc Update sbt-multi-jvm plugin to 0.3.8 and add sbt 0.13 docs
Merge pull request #1743 from akka/wip-upgrade-sbt-multijvm-ban

=pro,doc Update sbt-multi-jvm plugin to 0.3.8 and add sbt 0.13 docs
Merge remote-tracking branch: upstream/master