Numpy requirements version

[raphaelsty]

Hi team 😀

I regularly encounter the error ImportError: numpy.core.multiarray failed to import when I install river, in google collab and on my computer.

This error appears during the installation of river when you have a version of numpy <= 1.19.0. Also I encountered the problem with the latest version of river 0.9.0.

The command pip install -U numpy solves the problem immediately of course.

Do you think it would be wise to update the requirements of river with at least the 1.20.0 version of numpy? Is there any inconvenience to move to a newer version of numpy?

Complete logs:

Traceback:
__init__.pxd:943: in numpy.import_array
    ???
E   RuntimeError: module compiled against API version 0xe but this version of numpy is 0xd

During handling of the above exception, another exception occurred:
../../../opt/miniconda3/envs/cherche/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
cherche/retrieve/__init__.py:7: in <module>
    from .tfidf import TfIdf
cherche/retrieve/tfidf.py:7: in <module>
    from river import feature_extraction
../../../opt/miniconda3/envs/cherche/lib/python3.8/site-packages/river/__init__.py:9: in <module>
    from . import (
../../../opt/miniconda3/envs/cherche/lib/python3.8/site-packages/river/ensemble/__init__.py:10: in <module>
    from .adaptive_random_forest import (
../../../opt/miniconda3/envs/cherche/lib/python3.8/site-packages/river/ensemble/adaptive_random_forest.py:9: in <module>
    from river import base, metrics, stats, tree
../../../opt/miniconda3/envs/cherche/lib/python3.8/site-packages/river/metrics/__init__.py:35: in <module>
    from .expected_mutual_info import expected_mutual_info
build/lib.macosx-10.9-x86_64-3.7/river/metrics/expected_mutual_info.pyx:11: in init river.metrics.expected_mutual_info
    ???
__init__.pxd:945: in numpy.import_array
    ???
E   ImportError: numpy.core.multiarray failed to import

[MaxHalford]

Thanks for suggesting this! I think it's a good idea. I'll let you open a PR :)