Add rewrite test as method to vc

Change-Id: I87ac48fdbf9d4c75ce09c4456460d1ede56b9034
diff --git a/dev/js/src/vc/jsonld.js b/dev/js/src/vc/jsonld.js
index 545652b..600a5bb 100644
--- a/dev/js/src/vc/jsonld.js
+++ b/dev/js/src/vc/jsonld.js
@@ -95,6 +95,10 @@
       };
     },
 
+    rewrites : function () {
+      return null;
+    },
+
     toQuery : function () {
       return '';
     }