Updated version of Sbt dependencies

Updated version of Sbt dependencies to 0.13.0-RC3-SNAPSHOT (when building
against Scala 2.10.3-SNAPSHOT), and 0.13.1-SNAPSHOT (when building against
Scala 2.11.0-SNAPSHOT).  The odd version number is due to the fact that we
rebuild Sbt artifacts every night against the latest Scala 2.10.3-SNAPSHOT and
2.11.0-SNAPSHOT, and hence the trailing SNAPSHOT is needed to make Maven happy.