Need forward and transparent proxy examples in documentation

[izrik]

Copied from https://github.com/rackerlabs/deproxy/issues/69 by @baynes

As far as I can make out all the examples are for reverse proxies (the proxy looks like a normal website to the client, but one that gets the data to return by making further accesses behind the scenes). However I want to test a forward proxy (the web client uses its proxy settings to explicitly ask the proxy to get a certain page from some other web server) or a transparent proxy (the client thinks it is talking to the target web server but the proxy has intercepted the communication and is then making the request to the actual target). I cannot see how to do either of these or even if it is supported.