Remove Orator ORM which is no longer maintained

Author: pei-lun

README.md

@@ -771,7 +771,6 @@ Inspired by [awesome-php](https://github.com/ziadoz/awesome-php).
     * [SQLAlchemy](https://www.sqlalchemy.org/) - The Python SQL Toolkit and Object Relational Mapper.
         * [awesome-sqlalchemy](https://github.com/dahlia/awesome-sqlalchemy)
     * [dataset](https://github.com/pudo/dataset) - Store Python dicts in a database - works with SQLite, MySQL, and PostgreSQL.
-    * [orator](https://github.com/sdispater/orator) -  The Orator ORM provides a simple yet beautiful ActiveRecord implementation.
     * [orm](https://github.com/encode/orm) - An async ORM.
     * [peewee](https://github.com/coleifer/peewee) - A small, expressive ORM.
     * [pony](https://github.com/ponyorm/pony/) - ORM that provides a generator-oriented interface to SQL.