add to documentation: site admin (user 0) always sees default options

hi guys,

thanks for sharing this great module.

minor thing that had me stumped. i.e. when adjusting defaults and setting the "hide from form" option, I thought it wasn't working until I used masquerade to login as a site editor. In other words the site admin (user zero) will always see the default options.

maybe add that to the documentation?

dub