ExitPolicy Class for stem
"Arm has a readily available class for representing a Tor exit policy ( in torTools.py). We need to adapt this class to stem's coding styles, write a constructor for it (see the getExitPolicy() and getRelayExitPolicy() methods for examples), and see if we can improve on it. This will also need quite a bit of testing.."
Preliminary stab at this - Just to make sure I'm going in the right direction.