Add auth.

README.md

 * [OAuth2 Server](https://bshaffer.github.io/oauth2-server-php-docs/) - Another OAuth2 server implementation.
 * [OAuth2 Server](https://oauth2.thephpleague.com/) - An OAuth2 authentication server, resource server and client library.
 * [Opauth](https://github.com/opauth/opauth) - A multi-provider authentication framework.
+* [Paseto](https://github.com/paragonie/paseto) - Platform-Agnostic Security Tokens.
 * [PHP oAuthLib](https://github.com/Lusitanian/PHPoAuthLib) - Another OAuth library.
 * [Sentinel Social](https://cartalyst.com/manual/sentinel-social/2.0) - A library for social network authentication.
 * [Sentinel](https://cartalyst.com/manual/sentinel/2.0) - A framework agnostic authentication & authorisation library.