Bump xstream from 1.4.15 to 1.4.16

diff --git a/pom.xml b/pom.xml
index ffa50e1..e8ad908 100644
--- a/pom.xml
+++ b/pom.xml
@@ -173,7 +173,7 @@
     <dependency>
       <groupId>com.thoughtworks.xstream</groupId>
       <artifactId>xstream</artifactId>
-      <version>1.4.15</version>
+      <version>1.4.16</version>
     </dependency>
     <dependency>
       <groupId>org.apache.commons</groupId>