Add a setup.cfg file

Based on https://github.com/pypa/sampleproject/blob/master/setup.cfg

Issue #5 (#5)

setup.cfg

@@ -0,0 +1,12 @@
+[metadata]
+# This includes the license file in the wheel.
+license_file = LICENSE.txt
+
+[bdist_wheel]
+# This flag says to generate wheels that support both Python 2 and Python
+# 3. If your code will not run unchanged on both Python 2 and 3, you will
+# need to generate separate wheels for each Python version that you
+# support. Removing this line (or setting universal to 0) will prevent
+# bdist_wheel from trying to make a universal wheel. For more see:
+# https://packaging.python.org/guides/distributing-packages-using-setuptools/#wheels
+# universal=1