The leader is responsible for every update

[Guergeiro]

Now Followers memory is updated by Leader!

• Added new param to ComunicationMessage, which contains the payload from the Leader. It can be empty. This param is actually an ArrayList that contains all places from the Leader.
• When Followers receive a Leader heartbeat, they check if it contains a payload. If it does, it swaps it's own ArrayList for the one that came from the Leader.
• This closes #6.

To test this you can use the example bellow. Leader needs to be on Port: 6001 and Follower on Port: 6002:

public static void main(String[] args) throws MalformedURLException, RemoteException, NotBoundException, InterruptedException {

    PlacesListInterface leader = (PlacesListInterface) Naming.lookup("rmi://localhost:6001/placelist");

    leader.addPlace(new Place("3600", "Viseu"));

    Thread.sleep(5000);

    PlacesListInterface follower = (PlacesListInterface) Naming.lookup("rmi://localhost:6002/placelist");

    Place place = follower.getPlace("3600");

    System.out.println(place);
  }

[Guergeiro]

@diogofalken It seems that round robing keeps getting you...

[Guergeiro]

I will merge this pull request since the feature that it implements is working. A new bug was found (#17) and will be fixed in the future.