Added Microdata class and test

Microdata class allows creating MicrodataParser from different sources.

src/Microdata.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace YusufKandemir\MicrodataParser;
+
+abstract class Microdata
+{
+    public static function fromHTML($html, $documentURI = '')
+    {
+        $dom = new \DOMDocument;
+        $dom->loadHTML($html, LIBXML_NOERROR);
+        $dom->documentURI = $documentURI;
+
+        return new MicrodataParser($dom);
+    }
+
+    public static function fromHTMLFile($filename, $documentURI = '')
+    {
+        $dom = new \DOMDocument;
+        $dom->loadHTMLFile($filename);
+        $dom->documentURI = $documentURI;
+
+        return new MicrodataParser($dom);
+    }
+
+    public static function fromDOMDocument(\DOMDocument $dom)
+    {
+        return new MicrodataParser($dom);
+    }
+}