Bump version number to 2.4.0

Author: RedFantom

setup.py

@@ -28,7 +28,7 @@ def read(fname):
     name='ttkthemes',
     packages=['ttkthemes'],
     package_data={"ttkthemes": ["themes/*"]},
-    version='2.3.0',
+    version='2.4.0',
     description='A group of themes for the ttk extensions of Tkinter with a Tkinter.Tk wrapper',
     author='The ttkthemes authors',
     author_email='redfantom@outlook.com',