Correct liftsh bootstrapping for new sbt.

It looks like sbt changed their download location and the amount of work
we have to do to bootstrap the liftsh script. This resolves those
differences.

liftsh

@@ -2,13 +2,17 @@
 
 # Make sure to change the name of the launcher jar and the source when bumping sbt version
 # so that the existence test below fails and we download the new jar.
-SBT_LAUNCHER_PATH="project/sbt-launch-0.13.5.jar"
-SBT_LAUNCHER_SOURCE="http://repo.typesafe.com/typesafe/ivy-releases/org.scala-sbt/sbt-launch/0.13.5/sbt-launch.jar"
+SBT_LAUNCHER_PATH="project/sbt-launch-0.13.8.jar"
+SBT_LAUNCHER_SOURCE="https://dl.bintray.com/sbt/native-packages/sbt/0.13.8/sbt-0.13.8.tgz"
 
 # Download the sbt launcher on-the-fly if it's not already in the repository.
 if test ! -f $SBT_LAUNCHER_PATH; then
+  BASEDIR=$(dirname $SBT_LAUNCHER_PATH)
   echo "Downloading sbt launcher..."
-  curl -o ${SBT_LAUNCHER_PATH} ${SBT_LAUNCHER_SOURCE}
+  curl -L -o ${SBT_LAUNCHER_PATH}.tgz ${SBT_LAUNCHER_SOURCE}
+  tar xf $SBT_LAUNCHER_PATH.tgz -C $BASEDIR
+  mv $BASEDIR/sbt/bin/sbt-launch.jar $SBT_LAUNCHER_PATH
+  rm -rf $BASEDIR/sbt
 fi
 
 # Load custom liftsh config