Change ad_banner preview from using title to id

app/assets/javascripts/inc/modal-preview.js

@@ -7,9 +7,7 @@ $(document).ready(function() {
 		$(this).after("<span id='show_preview'></span>");
 		$.ajax({
 			type: 'PUT',
-			//async : true,
 			url:$(this).attr("href"),
-			contentType: 'application/javascript; charset=utf-8',
 			data:$(this).parents("form").serialize(),
 			success: function (msg) {
 					$("#"+start_modal_with_id).modal('show'); },