Path as callback fix

Currently in the docs you specify that you may do a callback for the path, example:

```html
<div id="rate" data-path="assets/raty/"></div>
```
```js
$('#rate').raty({
    path : function() {
        return $(this).data('path');
    }
});
```

This however currently does not work. It creates this error `TypeError: this.opt.path.charAt is not a function` because its expecting a string but its instead a function.

This pull request simply adds `path` to your `_adjustCallback` method and all works as it should.