use latest sbt launching script

https://github.com/paulp/sbt-extras/blob/71b6f28462bd0e555a99568248a9ac2b5370e581/sbt
upgrade to sbt 0.13
use sbt 0.13 macro syntax
use pack200 from JAVA_HOME in build
Merge pull request #99 from NetLogo/sbt-0.13

upgrade to sbt 0.13