Change buildUrl to support https

Add an argument to buildUrl to make it support https

Author: JellyBool

src/Qiniu/Processing/Operation.php

@@ -44,13 +44,13 @@ public function execute($key, $fops)
         return array($resp->body, null);
     }
 
-    public function buildUrl($key, $fops)
+    public function buildUrl($key, $fops，$protocol = 'http')
     {
         if (is_array($fops)) {
             $fops = implode('|', $fops);
         }
 
-        $url = "http://$this->domain/$key?$fops";
+        $url = $protocol."://$this->domain/$key?$fops";
         if ($this->auth !== null) {
             $url = $this->auth->privateDownloadUrl($url, $this->token_expire);
         }