add javadoc

Author: Anh Dung Bui

src/main/java/org/joo/promise4j/PipeAlwaysCallback.java

@@ -3,7 +3,7 @@
 /**
  * Represents a pipe for fulfilled promise. Pipe is similar to filter, except
  * that they returns a {@link org.joo.promise4j.Promise} instead of the result.
- * 
+ *
  * @author griever
  *
  * @param <D> the response type when the promise is fulfilled
@@ -14,8 +14,10 @@ public interface PipeAlwaysCallback<D, D_OUT, F extends Throwable, F_OUT extends
 
     /**
      * A callback to be called when the promise is fulfilled.
-     * 
-     * @param result the result of the promise
+     *
+     * @param status the status of the promise
+     * @param result the result of the promise if any
+     * @param cause  the cause of the failure if any
      * @return the new promise
      */
     public Promise<D_OUT, F_OUT> onAlways(final DeferredStatus status, final D result, final F cause);