public class SubGraphRPermuterVersion2
Create all r-permutations of a graph given a set of $n>r$ vertex labels. This class should not be used to values of
$n$ that are very large! This is a (hopefully temporary) version that tries not to be clever. (Trying to rule out
sources of error.) CSC, 6/21/12
Not using this yet, though. I'm not sure it is correct.