fallback for productive hosting like gunicorn / nginx

[blodone]

No description provided.

[coveralls]

Coverage remained the same at 93.92% when pulling 1b3bdf5 on induux:master into 555144f on Bouke:master.

[Bouke]

Thanks for contributing. However, someone could spoof the X-Forwarded-For header. So using any of those information provided by the client should be a conscious decision of the developer. If the website will run behind a proxy using any of those headers, that'd be fine, otherwise no magic should happen. See also issue #12 and #21 which try to 'address' the same issue.