Add runtime support: don't only listen on /tmp/frajtano1, script to add peer

lib/frajtano.ex

@@ -18,7 +18,7 @@ defmodule Frajtano.Supervisor do
   def init(:ok) do
   	children = [
   	  Frajtano.Agent,
-  	  {Frajtano.Listener, ["/tmp/frajtano1"]},
+  	  {Frajtano.Listener, [Application.fetch_env!(:frajtano, :listen_path)]},
   	  {Task.Supervisor, name: Frajtano.ClientSupervisor},
   	  {DynamicSupervisor, name: Frajtano.Peer}
   	]