Add ObjectStorage module.

js/storage.js

@@ -0,0 +1,25 @@
+'use strict';
+
+/** Allows to save objects to HTML5 local storage.
+ * However, it can only save properties, not functions.
+ */
+var ObjectStorage = (function() {
+  try {
+    var _s = localStorage;
+    return {
+      save: function(key, item) {
+        _s.setItem(key, JSON.stringify(item));
+      },
+      load: function(key) {
+        return JSON.parse(_s.getItem(key));
+      }
+    };
+  } catch (e) {
+    alert('There is no local storage for you.'
+      + ' If you refresh the page, all progress will be lost');
+    return {
+      save: function(key, item) {},
+      load: function(key) { return null; }
+    };
+  };
+});