OS X fix, Makefile

Found some people having trouble with this on OS X, added a check to the path-guesser that guesses right by default. Also added a Makefile so people don't need to wonder whether there's anything more to it than "javac *.java", and because many people don't know how to use jar. (Me among them.)

Didn't include updated .class files because I don't know whether there's anything more to it.