style(rxPaginate): Hide disabled pagination links

Fixes #519.

After looking at patterns for pagination (and some encouragement from @klamping !), I decided just to hide any disabled links. There's no reason to display them, as they don't provide context and instead just add to the amount of info that the user needs to digest.

Went with `opacity: 0', since 'display: none` can be costly and messes up the alignment when disabled links are present.