* WARNING : There are two backward incompatible changes in this release.
- Slider now returns value => x as as value instead of slider => array(value => x)
- #value2 is removed and now for range sliders you should pass #default_value => array('value1' => 1, 'value2' => 50) for non ranged slider you can simply pass the number (no array needed)
* Invalid value when used as field widget fixed
* slider now return [value] instead of [slider][value] when submitted
