Use jQuery's .prop() and add disableAutoStyle option

As of jQuery 1.6 element properties should be accessed with jQuery's .prop() method (715a34623390fdc706968e4666d060e29728cd4f)

When coming from an earlier jQuery-selectBox version (I came from 1.0.6) setting inline styles overwrites existing css definitions. (4773a31efb48bac537e40f3df1174b7fbbc9cc1f)