Support X-Forwarded-For, and deploy to demo server

[tonyg]

As per http://twitter.com/miyagawa/status/3099517925: "does reversehttp.net demo server always send requesting-client as 127.0.0.1? Seems like a bug with proxy and stuff?"

I need to check to see what's happening.

Thanks to @miyagawa for the report!

[tonyg]

Indeed, on www.reversehttp.net, it always reports 127.0.0.1 as the requesting client IP address. It does work properly when I run it locally, however. The reason is as @miyagawa suspected - I'm running a reverse-proxy on port 80 on the demo server that isn't bright enough to include an X-Forwarded-For header. Possible solutions: switch to a smarter proxy and read the X-Forwarded-For header; or move to running on port 80 directly.

[tonyg]

Note -- it seems clear that support for X-Forwarded-For on the reversehttp leg should be automatic, but what about the relayhttp leg? My instinct is to not have it automatically enabled there; see http://en.wikipedia.org/wiki/X-Forwarded-For