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
run the NetLogo language tests (TestCommands/Reporters)
trivial code improvement
in command tests support "T>" "P>" "L>"

and note that a lot more tests pass now
fix 'sum []' to report 0 instead of blowing up
fix 'mod' to handle negative numbers right
fix handling of 'nobody' in language testing
if a test is expected to fail but doesn't, fail

needs an updated NetLogo jar because we need the fix to Finder
in NetLogo/NetLogo@07de02783856696f108313bb4e62f6e802e82582)
Merge remote-tracking branch 'origin/master' into sbt-0.13.1

Conflicts:
	tortoise.sh
throw a better error message when command tasks are used
don't allow canceled tests to also have redundant excuses
minor code improvement
in engine, fix equality to be recursive
adjust default world dimensions to match NL

making more tests pass, yay!
fix how 'random' handles negative numbers
reclassify some failing command tests
work around sbt 0.13.1 regression