swagger-express does not work behind reverse proxy

It is a normal practice to deploy REST services behind reverse proxies in production. But swagger-express will fail to work currently. The problem is that swagger json is bound to basePath prefix.

We came up with these fixes which did the job for us:
https://gist.github.com/RomanKisilenko/74ab3ff697696ba7eb07062834e4b022

Hopefully you can integrate these changes and release next version.
