Consider preparing for CloudFront nightmares

[toolness]

This app really doesn't need tons of caching because it's going to have so little traffic, but if it ends up being hosted somewhere other than a subdomain of app.cloud.gov, that means it's going to be fronted by CloudFront, which means nightmares. See e.g.:

• https://github.com/18F/calc/issues/1257
• https://github.com/18F/calc/pull/1260
• https://github.com/18F/calc/issues/1516
• https://github.com/18F/calc/issues/1198#issuecomment-270492352

We might also want to use Whitenoise's compressed manifest static file storage so that it gives every static asset a unique URL based on its hash. Or we could just tell whitenoise to serve its static assets with max-age=0 too, I guess.