Caching issues
- Expires value needs to be a RFC 1123 date http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.21
- maxAge needs to be defined in seconds. It's used by express-session to set cookie's max-age value (https://www.ietf.org/rfc/rfc2109.txt).
- Modern browsers prefer Cache-Control header over Expires header.
- Pragma is obsolete: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.32
