change json3 to json2, which seems more compatible with old browsers

Author: warpech

index.html

@@ -26,7 +26,7 @@
 	</style>
 
 	<script src="jquery.handsontable.js"></script>
-	<script src="lib/json3.min.js"></script><!-- Only needed by index.html for IE6/IE7 support. Not needed by jquery.handsontable.js -->
+	<script src="lib/json2.min.js"></script><!-- Only needed by index.html for IE6/IE7 support. Not needed by jquery.handsontable.js -->
 	<link rel="stylesheet" media="screen" href="jquery.handsontable.css">
 </head>