force a feed refresh when someone subscribes

src/main/java/com/commafeed/backend/feeds/FeedRefreshWorker.java

@@ -69,7 +69,16 @@ public class FeedRefreshWorker {
 		}
 		return new AsyncResult<Void>(null);
 	}
-
+	
+	@Asynchronous
+	public void updateAsync(Feed feed){
+		try {
+			update(feed);
+		} catch (Exception e) {
+			log.error(e.getMessage(), e);
+		}
+	}
+	
 	private void update(Feed feed) throws NotSupportedException,
 			SystemException, SecurityException, IllegalStateException,
 			RollbackException, HeuristicMixedException,