Fixed .disabled display; added .done style.

.disabled won't react to the mouse at all, instead of changing colors & cursor & whatnot.
.done is a middle ground between regular and :hover states. It is different from regular and still reacts on hover, good when you want to visually separate future and past steps of the wizard.
Merge pull request #2 from schonarth/master

Fixed .disabled display; added .done style.