Issue #148: upgrade to checkstyle 8.9

Author: romani

README.md

@@ -14,6 +14,7 @@ This plugin provides coding rules from [Checkstyle](http://checkstyle.sourceforg
 
 Checkstyle Plugin|Sonar|Checkstyle|Jdk
 -----------------|-----|----------|---
+4.9|5.6.6|8.9|1.8
 4.8|5.6.6|8.8|1.8
 4.7|5.6.6|8.7|1.8
 4.6|5.6.6|8.6|1.8

pom.xml

@@ -85,7 +85,7 @@
   </ciManagement>
 
   <properties>
-    <checkstyle.version>8.8</checkstyle.version>
+    <checkstyle.version>8.9</checkstyle.version>
     <sonar.version>5.6.6</sonar.version>
     <sonar-java.version>3.7</sonar-java.version>
     <java.version>1.8</java.version>