Upgrade to Velocity 2.1

Fixes gh-68

Author: kazuki43zoo

pom.xml

@@ -74,7 +74,7 @@
     <dependency>
       <groupId>org.apache.velocity</groupId>
       <artifactId>velocity-engine-core</artifactId>
-      <version>2.0</version>
+      <version>2.1</version>
     </dependency>
     <dependency>
       <groupId>org.apache.commons</groupId>