The rows in these tables were using the styles from the `.poll`
selector, and the `position: relative` property defined there caused the
inner borders to disappear in some browsers (like Firefox).
So we're adding the `public` class to the selector; this way, it doesn't
affect elements in the admin section.
Even though it's only necessary to add the `.public` prefix to the
`.poll` selector in one place in order to fix this issue, we're doing it
everywhere for consistency.
This is consistent with the way we've got partials to render debates,
proposals and legislation processes on their index pages.
Note that, while adding the tests for the status icon, we're keeping one
system test because it also tests the process of voting. We're adding a
new, similar component test, where the voter is created in the database,
so all possible statuses are tested in the component.
