Use MaterialRow for MaterialMasonry.

Author: BenDol

src/main/java/gwt/material/design/addins/client/masonry/MaterialMasonry.java

@@ -55,7 +55,7 @@
  * @author kevzlou7979
  */
 //@formatter:on
-public class MaterialMasonry extends MaterialWidget {
+public class MaterialMasonry extends MaterialRow {
 
     static {
         if(MaterialAddins.isDebug()) {