Compass - all containers should be rendered conditionally if no content passed

[nicolethoen]

Footer - the footer always renders a div, even if nothing is passed through this prop to Compass. Even if visually empty, this causes an extra grid gap spacing above where the empty footer wrapper is - conditionally removing this if nothing exists would remove the unneeded space. I imagine this same issue would apply if a user didn't use another layout component, such as a sidebar on one side.