how to emit full path from watched directory?

@SuperEvenSteven

``` java
public class DirectoryEvent {
public final File dir;
public final WatchEvent event;
public DirectoryEvent(File dir, WatchEvent event) {
this.dir = dir;
this.event = event;
}
}

public static Observable events(File dir) {
return FileObservable.from(dir).map(event -> new DirectoryEvent(dir, event));
}
```