add enum wrapper (#375)

Author: shmax

src/JsonSchema/ConstraintError.php

@@ -4,7 +4,7 @@
 
 use JsonSchema\Exception\InvalidArgumentException;
 
-class ConstraintError extends \MabeEnum\Enum
+class ConstraintError extends Enum
 {
     const ADDITIONAL_ITEMS = 'additionalItems';
     const ADDITIONAL_PROPERTIES = 'additionalProp';

src/JsonSchema/Enum.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace JsonSchema;
+
+abstract class Enum extends \MabeEnum\Enum
+{
+}