update maven-plugin-plugin version
update maven-plugin-plugin version

```
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.7:jar (attach-javadocs) on project scalaxb-maven-plugin: MavenReportException: Error while creating archive:
[ERROR] Exit code: 1 - /Users/eed3si9n/work/scalaxb/mvn-scalaxb/src/main/java/org/scalaxb/maven/AbstractScalaxbMojo.java:313: warning: no @return
[ERROR]     protected List<String> arguments() {
[ERROR]                            ^
```

eed3si9n/scalaxb,eed3si9n/scalaxb,eed3si9n/scalaxb