updated m-estimate docs.

Author: Pal Westenthanner

category_encoders/m_estimate.py

@@ -109,7 +109,7 @@ def __init__(self, verbose=0, cols=None, drop_invariant=False, return_df=True,
 
     # noinspection PyUnusedLocal
     def fit(self, X, y, **kwargs):
-        """Fit encoder according to X and binary y.
+        """Fit encoder according to X and binary or continuous y.
 
         Parameters
         ----------