Adding support to only show appropriate languages on supported services

This change introduces a dictionary which maps docs to languages. I'll make the list fully functional when we are confident in this approach.

Relevant changes are at https://github.com/rackerlabs/developer.rackspace.com/compare/dev...gh-206#diff-c669c82f2dfb340df8af5584cb9ad589R4

- Fixes #206
> It's not like these are going to change often. I think this (for now) is a case of where good > best.

:+1: That's fine - I'm just brainstorming here.

Although, changing infrequently is exactly why I'd like to see it automated: I can guarantee that we won't remember to keep it up to date when service availability *does* change.