Upgrade to maven-checkstyle-plugin 2.14

Release notes:

http://mail-archives.apache.org/mod_mbox/maven-announce/201409.mbox/%3C1430082.PcumKFdX1o%40herve-desktop%3E
http://mail-archives.apache.org/mod_mbox/maven-announce/201502.mbox/%3C1986811660.01423169180947.JavaMail.Dennis%40Dennis-Dator%3E

pom.xml

@@ -74,7 +74,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-checkstyle-plugin</artifactId>
-        <version>2.12.1</version>
+        <version>2.14</version>
         <executions>
           <execution>
             <id>check</id>