Fixed JavaDocs Warnings

Author: kevzlou7979

src/main/java/gwt/material/design/addins/client/overlay/MaterialOverlay.java

@@ -121,7 +121,6 @@ public void close() {
 
     /**
      * Get source widget for path animator
-     * @return
      */
     public MaterialWidget getSource() {
         return source;

src/main/java/gwt/material/design/addins/client/waterfall/MaterialWaterfall.java

@@ -52,7 +52,7 @@
  *          <m:MaterialAnchorButton text="Get Started" size="LARGE" backgroundColor="blue lighten-2" textColor="white"/>
  *      </m:MaterialPanel>
  * </ma:waterfall.MaterialWaterfall>
- *
+ * }
  * </pre>
  *
  * @author kevzlou7979

src/main/java/gwt/material/design/addins/client/window/MaterialWindow.java

@@ -181,7 +181,7 @@ protected JsDragOptions buildDragOptions() {
 
     /**
      * Override to provide custom {@link MaterialDnd} instance. Default implementation will construct {@link MaterialDnd}
-     * using options provided by {@link {@link #buildDragOptions()} and will ignore drag events from content portion of
+     * using options provided by {@link #buildDragOptions()} and will ignore drag events from content portion of
      * the window ({@link AddinsCssName#CONTENT}) as well from action buttons (close, maximize and other {@link AddinsCssName#WINDOW_ACTION}.
      */
     protected MaterialDnd buildDnd() {