This PR addresses #597 as well as some other thing by the way, like:

• port overriding - it turned out it was not entirely possible. I also updated documentation with necessary informations of how to do it.
• it makes it possible to reset default port, which might be useful while debugging using ngrok proxy, where simple link proxies to proper port on localhost and thus connection URL doesn't need additional port.

By introducing above changes it also became possible to inspect staging applications if necessary, by proxying devtools middleware through ngrok. Just as with HTTPS on localhost :)