Fix pQuery classes to respect psr-4

lib/Util/pQuery/DomNode.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace MailPoet\Util\pQuery;
+
+class DomNode extends \pQuery\DomNode {
+  public $childClass = 'MailPoet\Util\pQuery\DomNode';
+
+  function getInnerText() {
+    return html_entity_decode($this->toString(true, true, 1), ENT_NOQUOTES, 'UTF-8');
+  }
+
+  function getOuterText() {
+    return html_entity_decode($this->toString(), ENT_NOQUOTES, 'UTF-8');
+  }
+}