Checkstyle 2.17 -> 3.0.0.

Author: Gary Gregory

pom.xml

@@ -280,7 +280,7 @@ file comparators, endian transformation classes, and much more.
     </commons.osgi.export>
     <commons.scmPubUrl>https://svn.apache.org/repos/infra/websites/production/commons/content/proper/commons-io/</commons.scmPubUrl>
     <commons.scmPubCheckoutDirectory>site-content</commons.scmPubCheckoutDirectory>
-    <checkstyle.plugin.version>2.17</checkstyle.plugin.version>
+    <checkstyle.plugin.version>3.0.0</checkstyle.plugin.version>
     <commons.jacoco.version>0.8.4</commons.jacoco.version>
     <commons.surefire.version>2.22.2</commons.surefire.version>
     <commons.japicmp.version>0.14.1</commons.japicmp.version>