upgrade sbt launch script

this is paulp/sbt-extras, commit
40c502ffe9f3e645dc6b4a4b1582e216da51222f
upgrade to sbt 0.13.5-RC1
upgrade to sbt 0.13.5-RC2
upgrade to sbt 0.13.5-RC3
upgrade to sbt 0.13.5-RC4
upgrade to sbt 0.13.5
upgrade to Scala 2.11.1
upgrade to ScalaTest 2.2.0-RC1
Merge branch 'master' into scalatest-2.2