added 'addNote' method to MergeRequests API

Author: alfredbez

lib/Gitlab/Api/MergeRequests.php

@@ -153,6 +153,19 @@ public function showNotes($project_id, $mr_id, $page = 1, $per_page = self::PER_
         return $this->getList($project_id, null, $page, $per_page, $order_by, $sort, 'merge_requests/'.$this->encodePath($mr_id).'/notes');
     }
 
+    /**
+     * @param int $project_id
+     * @param int $mr_id
+     * @param string $note
+     * @return mixed
+     */
+    public function addNote($project_id, $mr_id, $note)
+    {
+        return $this->post($this->getProjectPath($project_id, 'merge_request/'.$this->encodePath($mr_id).'/notes'), array(
+            'body' => $note
+        ));
+    }
+
     /**
      * @param int $project_id
      * @param int $mr_id