改善拖拽组件不好拖动的情况

@@ -26,6 +26,7 @@ var jQuery = require('jquery');
 
             var placeholder = $('<' + items[0].tagName + ' class="sortable-placeholder">');
             placeholder.css("border","2px dashed red");
+            placeholder.css("height",$(items[0]).height());
 
             var handle = options.handle, isHandle;
             items.find(handle).mousedown(function() {