add setUserAgent support

src/Crawler.php

@@ -28,6 +28,10 @@ class Crawler{
         $this->crawler->setCrawlProfile(new CrawlAllUrls());
     }
 
+    public function setUserAgent($agent){
+        $this->crawler->setUserAgent($agent);
+    }
+
     public function crawl($url){
         $this->crawler->startCrawling($url);
     }