v1.8:
  (Steve):  fixed bug in EmulatedNodeServer.java.  Packet.MAX_PACKET_SIZE
            should have been EmulatorPacket.MAX_PACKET_SIZE

v1.7:

  (Steve):  fixed bug in Node.onReceive() spotted by Benjamin Hindman.
            Bug would call a method on an object reference before verifying
            the reference was non-null.

 (Safeer):  modified lib/Manager.java and lib/Packet.java so that
            if a node attempts to send a packet with TTL 0, the
            manager raises an exception