Added global "use strict";

Author: shospodarets

.jshintrc

@@ -12,6 +12,7 @@
 	"eqnull": true,
 	"expr": true,
 	"browser": true,
+    "globalstrict": true,
 	"predef": ["DEBUG",
 		"console",
 		"require",

dist/jquery.indexeddb.js

@@ -1,3 +1,4 @@
+'use strict';
 (function($, undefined) {
 	var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
 	var IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange;
@@ -42,7 +43,7 @@
 				var version = config.version;
 				if (config.schema && !version) {
 					var max = -1;
-					for (key in config.schema) {
+					for (var key in config.schema) {
 						max = max > key ? max : key;
 					}
 					version = config.version || max;