CLI docs needed

[brad]

Specifically we need documentation describing these items as explained in #18

• run the nokia script on a machine, where a browser is available
• callback does not need to be reachable from outside.

[magnific0]

Re: same machine to complete authorization and running the script. I think this is preferable (easiest), but not a necessity as long as:

1. callback_url points to the correct machine (use IP for simplicity)
2. the clients can connect to each other (e.g., no wireless isolation)
3. the port chosen is allowed, available and not firewalled.

There will be users that want to run the script on a headless machine. Looking at bin/nokia nothing seems to restrict it to a local only setup except the use of webbrowser to launch an instance, but the url is already printed anyway, so this step can be done manual.

Another idea entirely is to simply pick a non-existing callback (e.g., localhost:9999) and copy the code parameter from the address bar into the CLI. It's not elegant, but very simple and robust.