Use only one jQuery variable inside pretty photo gallery

A few jQuery functions like .map or .inArray are used this way:

```javascript
jQuery.inArray
```

As in Pretty Photo plugin a jQuery variable is passed using an anonymous function:

```javascript
(function($) {
    // plugin code
})(jQuery);
```

A safer option is to use $ variable all along the way inside a plugin code. It's very important when you deal with a few versions of jQuery at the same time on the single web page since it can take a jQuery version without .map function or something like that. The other reason is a consistency.