Upgrade to commons-parent version 21

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/cli/trunk@1152714 13f79535-47bb-0310-9956-ffa450edef68

Author: ebourg

pom.xml

@@ -19,7 +19,7 @@
   <parent>
     <groupId>org.apache.commons</groupId>
     <artifactId>commons-parent</artifactId>
-    <version>15</version>
+    <version>21</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <groupId>commons-cli</groupId>