Add the ability to specify options for the buttons.

It would be nice of .dialog({buttons: {}) accepted a buttonOptions for each of the buttons.

Example

$('#myDialog').dialog({
        buttons: [{
            text: 'Test',
            butttonOptions: { //Any valid .button options should be able to be passed here.
                icons: {
                    primary: 'ui-icon-disk'
                }
            }}]
    });

I see where the change to .dialog need to be done and will be submitting a pull request.