Make sure description shows up on pypi

Author: t-persson

setup.cfg

@@ -5,7 +5,7 @@ author = Tobias Persson
 author-email = [email protected]
 license = Apache License, Version 2.0
 home-page = https://github.com/eiffel-community/eiffel-pythonlib
-description-file = README.rst
+long_description = file: README.rst
 classifiers = Development Status :: 5 - Production/Stable
               Programming Language :: Python
               License :: OSI Approved :: Apache Software License