Update multi curl example in readme; Add multi curl examples

examples/multi_curl_delete.php

@@ -0,0 +1,17 @@
+<?php
+require '../src/Curl/Curl.php';
+require '../src/Curl/MultiCurl.php';
+
+use \Curl\Curl;
+use \Curl\MultiCurl;
+
+$multi_curl = new MultiCurl();
+
+$multi_curl->addDelete('https://httpbin.org/delete', array(
+    'id' => '123',
+));
+$multi_curl->addDelete('https://httpbin.org/delete', array(
+    'id' => '456',
+));
+
+$multi_curl->start();