Update demo.js

Added missing functions

js/AdminLTE/demo.js

@@ -70,3 +70,12 @@ $(function() {
     $("body").append(demo);
     $("body").append(demo_settings);
 });
+
+function change_layout() {
+    $("body").toggleClass("fixed");
+    fix_sidebar();
+}
+function change_skin(cls) {
+    $("body").removeClass("skin-blue skin-black");
+    $("body").addClass(cls);
+}