Upgrade to XMLUnit 2 (legacy)

diff --git a/pom.xml b/pom.xml
index 1533755..25ec427 100644
--- a/pom.xml
+++ b/pom.xml
@@ -176,9 +176,9 @@
     </dependency>
 
     <dependency>
-      <groupId>xmlunit</groupId>
-      <artifactId>xmlunit</artifactId>
-      <version>1.6</version>
+      <groupId>org.xmlunit</groupId>
+      <artifactId>xmlunit-legacy</artifactId>
+      <version>2.7.0</version>
       <scope>test</scope>
     </dependency>