[pkg] Configure "universal" wheel build According to https://packaging.python.org/distributing/#wheels, we should create universal wheels (no 2to3 step, no C extension). Configure this in setup.cfg. [ci skip]

--- a/setup.cfg	Mon Nov 21 15:17:32 2016 +0100
+++ b/setup.cfg	Mon Nov 21 14:52:33 2016 +0100
@@ -1,3 +1,6 @@
+[bdist_wheel]
+universal = 1
+
 [check-manifest]
 ignore =
   debian