Remove zones

@phamann this will make you happy

So it turns out we don't need to aggregate multiple tags. All we have to do is when we look up content for a section, instead look up the content for the section's tag. e.g., don't ask content api for 'culture', ask it for 'culture/culture'.

Articles in 'subsections' will have this section tag.

In order for this to work and for us not to cross the line of making more than one query per response we have to cache all the sections in memory. This isn't too bad, though - as we only have 67, it's a single request to Content API at start up to get them and stick them in an agent.