#58 Enable passthrough when upstream proxy isn't present.

[Justin Julicher]

It would be great to enable passthrough when the proxy isn't available on the network.

example of usage - I have a work laptop with this installed and when I go home I have to switch my configurations to go direct, although I do have a local proxy.pac file that does this for a number of applications that support this other applications that don't require a separate script that needs to be run.