:snake: Replace `attrs` with `dataclasses`

[evanroyrees]

Prior to dataclasses availability within the python standard library, attrs was used. This may be replaced now to reduce the requirements list.

Autometa/autometa/binning/unclustered_recruitment.py

Lines 76 to 86 in baf61c0

	@attr.s(auto_attribs=True)
	class TrainingData:
	features: pd.DataFrame = attr.ib(validator=validate_training_data)
	target: pd.DataFrame = attr.ib(validator=validate_training_data)
	target_names: List[str]
	@attr.s(auto_attribs=True)
	class Labels:
	target: pd.DataFrame
	target_names: List[str]

Autometa/make_test_data.py

Lines 99 to 100 in baf61c0

	@attr.s(auto_attribs=True)
	class TestData:

Autometa/autometa-env.yml

Line 7 in baf61c0

- attrs # test-data requirement

This is incorrectly labeled as a test-data requirement (it is, but attr is also used with the autometa-unclustered-recruitment module)