Pass user id for comment from $param

In comment_sync function user_id is available in argument $param, for API development we need to pass this user id, as there is no value returned for get_current_id() in https://github.com/rtCamp/rtMedia/blob/master/app/main/controllers/media/RTMediaComment.php on line 64
Merge pull request #495 from UmeshSingla/patch-6

Pass user id for comment from $param ( required for API developments )