Adding a ReactiveNavigator to handle toActivityForResult in an Observable way

The aim of this component is to handle the navigation to an Activity for result using an Observable and thus avoiding the need to check for result/response code and all the boilerplate code related.
Would it be simpler/clear to do something along the lines of:

```
Observable.defer(() -> {
	activityStarter.startActivityForResult(intent, requestCode);
	return onActivityResultSubject
})
.filter(result -> result.getRequestCode == requestCode)
```