Fix shortcut

This fixes the bug reported in #96 there was a typo in translation from python.  The current code was tested on 100 100 vertex Erdos Renyi graphs (p=0.1) against an implementation of the naive Bron Kerbosch algorithm.   

It also adds types to the sets as discussed in #95.  This should probably be a separate PR, but the two fixes are sufficiently trivial, so this shouldn't be a problem.  This along with the recent fixes to Set should speed things considerably.