Add failing test for '0 CODE.RAND'
Make '0 CODE.RAND' a no-op

Fixes #3, discovered by @asartalo
Document Interpreter.StackOK
Fix copy&paste bug
Make sure that MIN-RANDOM-{FLOAT,INTEGER} is <= MAX-RANDOM-{FLOAT,INTEGER}
Make '(NAME.RANDBOUNDNAME)' a no-op.

Fixes #2