add sklearn dependency (#298)

Author: s-scherrer

setup.cfg

@@ -45,6 +45,7 @@ install_requires =
     cadati>=0.0.2
     Cython>=0.29.21
     numba
+    scikit-learn
 # The usage of test_requires is discouraged, see `Dependency Management` docs
 # tests_require = pytest; pytest-cov
 # Require a specific Python version, e.g. Python 2.7 or >= 3.4