Bump dev version to 4.28.0

Author: markotoplak

setup.py

@@ -6,8 +6,8 @@
 from setuptools.command.install import install
 
 NAME = 'orange-widget-base'
-VERSION = '4.27.0'
-ISRELEASED = True
+VERSION = '4.28.0'
+ISRELEASED = False
 # full version identifier including a git revision identifier for development
 # build/releases (this is filled/updated in `write_version_py`)
 FULLVERSION = VERSION