v1.3.1

Restores the default_variator, default_mutator, and nondominated_cmp methods that were removed in 1.3.0, potentially breaking any code directly calling these methods. These methods are deprecated and will be removed in a future release, so we strongly recommend updating affected code.

1. Replace default_variator(...) with PlatypusConfig.default_variator(...)
2. Replace default_mutator(...) with PlatypusConfig.default_mutator(...)
3. Replace nondominated_cmp with nondominated_sort_cmp