Current instance status notification

* Add RefreshCallback so that custom instance status check logic can be implemented after getting an update from discovery.
* Add Cancel/Register support to MockRemoteEureakServer
* Add eureka-lifecycle project with a guide module for eureka bindings.
* Includes binding for an Rx Observable<Boolean> with running instance up status notification

Here is a usage example.  Note that the Observable is backed by a BehaviorSubject and as such emits the last known up status immediately after subscribe is called.  
```
    public static class Service {
        @Inject
        public Service(@UpStatus   Observable<Boolean> upStatusObservable) {
            upStatusObservable.subscribe(new Action1<Boolean>() {
                @Override
                public void call(Boolean status) {
                    System.out.println("***** Status changed to : " + status);
                }
            });
        }
    }
```