Index the "unimoney" campaign

https://www.pivotaltracker.com/story/show/76862090

At the moment, all artefacts of the "campaign" format are excluded from being indexed in search. 

We want to index the "unimoney" campaign in search, and we can do that by including this in the list of exceptional slugs.

Once this is deployed, there will be an additional step required to republish the campaign so that it will be inserted into the search index.