Topologies: Add distance and distancexy!
Tortoise: mark model docking tests as SlowTests
run `fast:test` from tortoise.sh. it doesn't take long
Merge pull request #465 from NetLogo/tortoise-distance

Topologies: Add distance and distancexy!
Merge remote-tracking branch 'origin/tortoise' into tortoise-timer

Conflicts:
	src/main/org/nlogo/tortoise/Strict.scala