18F/hub-pages-private submodule at pages/private

Pages from pages/private will not be generated for public version of the Hub.
How about hooking this up within [Travis](https://travis-ci.org/) or [CircleCI](https://circleci.com/) (the latter if you want it to automatically deploy, especially)? I'd also be interested in seeing a smoke test to check that a certain private page isn't present in the compiled site being deployed, to be really *really* sure it isn't in there.