2.11.2: Best to use a redirect URI with a port

Changed

• Updated the documentation to give more details on the authorization process and reflect
  2020 Spotify Application jargon and practices.
• The local webserver is only started for localhost redirect_uri which specify a port,
  i.e. it is started for http://localhost:8080 or http://127.0.0.1:8080, not for http://localhost.

Fixed

• Issue where using http://localhost as redirect_uri would cause the authorization process to hang.