Resolves #2: support for checkstyle to be run via maven

Because the latest maven checkstyle plugin uses checkstyle 5.7, I manually added a checkstyle 6.2 check.  When checkstyle supports java 8 fully in checkstyle 6.2+ then we can undo this.
It was from the checkstyle 6.2 tag of the checkstyle git repo.  It's unneeded now that I've resolved it with maven.  See the latest commit.