move copycat version property to root pom

Change-Id: I2422e67b077e2fbd5a6b51b35f41abe7b4287414
diff --git a/pom.xml b/pom.xml
index 7a81539..ee2a3bb 100644
--- a/pom.xml
+++ b/pom.xml
@@ -40,6 +40,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <netty4.version>4.0.23.Final</netty4.version>
+        <copycat.version>0.4.0-SNAPSHOT</copycat.version>
     </properties>
 
     <repositories>