fix javadoc plugin error during compilation on recent java versions (#52)

Author: nickrobson

pom.xml

@@ -177,7 +177,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>3.0.0-M1</version>
+                <version>3.0.1</version>
                 <configuration>
                     <quiet>false</quiet>
                     <sourcepath>${project.basedir}/src/main/delombok</sourcepath>