Updates to Code of Conduct

The existing Code of Conduct is modeled after CoC's used at conferences within the US. PWL is a loose confederation of meet-ups with an international reach and has slightly different needs. The updated CoC still explicitly states that PWL meetups and online communities should be harassment-free environments, but that it is up to the local organizers of live events to maintain that environment.
We should also add the freenode irc channel to this, #paperswelove.