Upgrade maven-javadoc-plugin to 3.0.1 (#519)

Author: chingor13

pom.xml

@@ -318,7 +318,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-javadoc-plugin</artifactId>
-          <version>2.9.1</version>
+          <version>3.0.1</version>
           <executions>
             <execution>
               <id>attach-javadocs</id>