Enable schema validation for the draft compliance tests

Author: erayd

tests/Drafts/Draft3Test.php

@@ -16,6 +16,9 @@
  */
 class Draft3Test extends BaseDraftTestCase
 {
+    protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    protected $validateSchema = true;
+
     /**
      * {@inheritdoc}
      */

tests/Drafts/Draft4Test.php

@@ -14,6 +14,9 @@
  */
 class Draft4Test extends BaseDraftTestCase
 {
+    protected $schemaSpec = 'http://json-schema.org/draft-04/schema#';
+    protected $validateSchema = true;
+
     /**
      * {@inheritdoc}
      */