Examples: fixes secure_auth_with_db.
Examples: fixes secure_auth_with_db.

 * Using the first element of the returned list of users in get_token(),
   because tinydb's db.search() always returns a list. This fixes
   a "TypeError: list indices must be integers, not str".
 * Refactors the variable "user" to always contain a single user dict,
   to be consistent.

timothycrosley/hug,MuhammadAlkarouri/hug,timothycrosley/hug,MuhammadAlkarouri/hug,timothycrosley/hug,MuhammadAlkarouri/hug