update changelog and version for release 2.4.0

Author: PaulWestenthanner

CHANGELOG.md

@@ -1,3 +1,15 @@
+v2.4.0
+======
+
+* improved documentation
+* fix bug in CatBoost encoder
+* fix future warnings with pandas
+* added tests for python 3.9 and 3.10 in pipeline
+* fix treating np.NaN and python None equal
+* only build docs on release
+* unified conversion of inputs pandas objects that are used internally including some bugfixes.
+* added quantile encoder and summary encoder
+ 
 v2.3.0
 ======
 

category_encoders/__init__.py

@@ -25,7 +25,7 @@
 from category_encoders.glmm import GLMMEncoder
 from category_encoders.quantile_encoder import QuantileEncoder, SummaryEncoder
 
-__version__ = '2.3.0'
+__version__ = '2.4.0'
 
 __author__ = "willmcginnis", "cmougan"