a note to disambiguate the mapping from "tunnel server" command to "tunnel" (not "server") parameter

[mfaulhab]

A suggestion to help N00bs:

In the readme, under Start tunnel, under Now set-up the tunnel:

Note: the "tunnel server" srv parameter in the wstunnel command from above goes in the "tunnel" parameter, not the "server" parameter for this command.
Hint: if your endpoint server complains of "GET /_tunnel" requests and your wstunnel cli command complains of "Error opening connection", you may have the parameters flipped and the tunnel pointing the wrong way.

[raphael]

Great suggestion, feel free to make a PR!