Update pom.xml

Revert back to 1.5.1

Author: kevzlou7979

gwt-material/pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <artifactId>gwt-material-parent</artifactId>
     <groupId>com.github.gwtmaterialdesign</groupId>
-    <version>1.5.2-SNAPSHOT</version>
+    <version>1.5.1</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 
@@ -46,4 +46,4 @@
       </plugin>
     </plugins>
   </build>
-</project>
+</project>