Document how to use JWT generated using CLI

[almstrand]

The CLI document describes how hz make-token 4C720BD1-2729-46BA-9213-ED84DEDE3120 can be used to generate a JWT.

The document used to also show how the user for which the JWT was generated can be added to the users table. This was removed in bcbc1a3de6.

Without this step, the JWT is of no use, and it appears not to be documented elsewhere that this is a required step, nor what should be the "schema" of the JSON documents in the users table.

The document used to say:

... you can create the user first:

 horizon('users').store({id: '4C720BD1-2729-46BA-9213-ED84DEDE3120'});

This was, in my opinion a very important piece of information. That said, I have come to find out (https://github.com/rethinkdb/horizon/issues/827) that a new user must also have a group property or the server will crash.

Could this be re-introduced to the document, with the added/required groups property? Perhaps something like:

... you can create the user first:

 horizon('users').store({id: '4C720BD1-2729-46BA-9213-ED84DEDE3120', groups: ['default', 'authenticated']});