upgrade to sbt-0.13.1-RC2
upgrade to sbt 0.13.1-RC3
make 'tortoise shell' script quieter on startup

using flag which is new in sbt 0.13.1
use 0.13.1-RC3 launcher too

0.13.0 launcher is supposed to work too, but let's not
take any chances
Merge remote-tracking branch 'origin/master' into sbt-0.13.1

Conflicts:
	tortoise.sh
work around sbt 0.13.1 regression
Merge pull request #51 from NetLogo/sbt-0.13.1

upgrade to sbt 0.13.1 (-RC3)