Prevent the friend rule from allowing an actor to be their own friend

As it stands now the `friends` rule is returning the actor themselves as a friend, since I believe they can satisfy both p1 and p2. I added a clause that p1 != p2, I think that's all that's necessary to fix it. Awesome use of edn for this, super easy to understand.

![screen shot 2014-01-05 at 6 22 45 pm](https://f.cloud.github.com/assets/239754/1847675/50748da6-7660-11e3-83d0-ed4d4e264cf3.png)