Changed the output

This commit changes the output. The new output, when the user is
authenticated is:
{
    "user": {
            id: 3,
            username: 'foo',
            lastname: 'fooo',
            ....
    },
    "courses" {
            "5":{
                    "name":"My first course",
                    "token":"caad14a34dc3582e1b0d9a83be6ae68b",
                    "startdate": date
                    ....
            },
            "7":{
              ....
            }
    }
}

This way the output contains both, user data and course data.
It is useful for mobile device because it gets the essential
data in one query.

Updated the Readme file.