Bump maven-javadoc-plugin from 2.10.2 to 3.1.0

Bumps [maven-javadoc-plugin](https://github.com/apache/maven-javadoc-plugin) from 2.10.2 to 3.1.0.
- [Release notes](https://github.com/apache/maven-javadoc-plugin/releases)
- [Commits](apache/maven-javadoc-plugin@maven-javadoc-plugin-2.10.2...maven-javadoc-plugin-3.1.0)

pom.xml

@@ -42,7 +42,7 @@
         <slf4j.version>1.7.25</slf4j.version>
         <akka-persistence-inmemory.version>0.2.1</akka-persistence-inmemory.version>
         <maven-gpg-plugin.version>1.6</maven-gpg-plugin.version>
-        <maven-javadoc-plugin.version>2.10.2</maven-javadoc-plugin.version>
+        <maven-javadoc-plugin.version>3.1.0</maven-javadoc-plugin.version>
         <nexus-staging-maven-plugin.version>1.6.8</nexus-staging-maven-plugin.version>
         <maven-source-plugin.version>2.4</maven-source-plugin.version>
         <coveralls-maven-plugin.version>3.1.0</coveralls-maven-plugin.version>