39204833 virus state

Displays the virus checking state using the file system and existence of files in certain folders, there is no live update so a page refresh is needed to see the file change state.

We hook into Edition::Publishing to block the publishing of a document, like we do with change notes if all attachments have yet to pass the virus checker.

Also display the file count in the tab, as a badge, because I was fed up of randomly opening editions looking to see if they had any attachments.

Fixes a ruby 2.0 replication with assert_raises

https://www.pivotaltracker.com/story/show/39204833