setup.cfg: Ensure setup.py is also skipped by testing.

Without this modification, running `nosetests` fails.

Author: jakirkham

setup.cfg

@@ -4,7 +4,7 @@ verbosity=3
 with-doctest=1
 doctest-tests=1
 with-coverage=1
-ignore-files=viewer.py
+ignore-files=setup.py|viewer.py
 [build_sphinx]
 builder=html
 [versioneer]