Elephas

- Raise an exception with a clear error message for developers using Tensorflow 2.13+ and an optimizer which is not a subclass of the `Optimizer` class from `tensorflow.keras.optimizers.legacy` (e.g; subclasses of `tensorflow.keras.optimizers`), as non-legacy optimizers cannot currently be serialized.

- Add support for distributed inference and evaluation of multiple input/output models: https://github.com/danielenricocahall/elephas/pull/34

- Added multiple input/multiple output training capabilities for `SparkModel`: https://github.com/danielenricocahall/elephas/pull/31

- Update to support Python 3.11 and consequently later Tensorflow versions (>2.10). This required changing the optimizer imports in the unit tests to use the legacy optimizer (`tf.keras.optimizers.legacy`), as detailed in [the corresponding PR](https://github.com/danielenricocahall/elephas/pull/25). For developers using a version of Tensorflow <2.11, importing from the optimizer package (`tf.keras.optimizers`) will still function as expected. Otherwise, the imports will need to be changed to the legacy optimizer to ensure your application doesn't break.

- Improve typehints for certain API functions
- Remove unused functions
- Refactor `utils.rdd_utils` to reduce actions (therefore improve performance) and improve readability/efficiency around creating or converting collections of `LabeledPoint`s

- Move over to [Poetry](https://python-poetry.org/docs/master/) for packaging and managing dependencies
- Refactor integration tests to remove non-deterministic connection errors
- Remove support for Python 3.7, as it will be [end-of-life](https://devguide.python.org/versions/) in 3 months
- Revise Tensorflow support to 2.3+, as older versions (2.0.x - 2.2.x) only support up to Python 3.7, according to the [compatibility tables](https://www.tensorflow.org/install/source#tested_build_configurations)
- Limit support up to Python 3.10, as Tensorflow versions we support aren't available yet in Python 3.11, according to the [compatibility tables](https://www.tensorflow.org/install/source#tested_build_configurations)