PyGAD 3.3.1

1. After the last generation and before the run() method completes, update the 2 instance attributes: 1) last_generation_parents 2) last_generation_parents_indices. This is to keep the list of parents up-to-date with the latest population fitness last_generation_fitness. #275
2. 4 methods with names starting with run_. Their purpose is to keep the main loop inside the run() method clean. Check the [Other Methods](https://pygad.readthedocs.io/en/latest/pygad.html#other-methods) section for more information.