Cache-Control header not set in Rails 5

[dylanfisher]

OK I think I got it working this time. Tested on Heroku against my fork and the correct headers are there.

If you're using Cloudfront you'll have to invalidate any cached assets after deploying.

Fixes #39

[brian-kephart]

Thanks. Is there a benefit to this method over the one used in #40?

[dylanfisher]

Moving the conditional out of the set_max_age method seems cleaner, but otherwise #40 is better since it preserves existing headers.

In this version if the cache_control method returns all headers I think it would be better.

I'm not sure if app.config.static_cache_control = cache_control needs to explicitly be set. I took that line out, which might be a mistake.

[humphreybc]

Could we get this merged?