Improved nginx.conf for Ruby On Rails

[Thomas]

> No.  All files that exists under root will be served by nginx itself.  Only
> non-existent urls will be proxied to backend.
>
Yeah I forgot to mention that the if statements were for rails apps
that use page caching.

@Andrew Loe: be very careful with your config file, I noticed you
defined server_name _; this can be dangerous depending on how your app
works. I have posted something about a potential security hole I have
more or less discovered this WE.