Force Spotlight::HomePage to be published.

We don't have a control to publish the home page so it has to
always be published. In the future we'll automatically generate
a home page on exhibit creation and we will also want the home
page to be auto-published then too.

@cbeer I think [this](https://github.com/sul-dlss/spotlight/blob/master/app/controllers/spotlight/home_pages_controller.rb#L19) is why the home page wasn't showing up in the demo today.