Use packages kwarg now that it's a package

Author: bgreen-litl

setup.py

@@ -31,7 +31,7 @@ def readme():
            version='1.4.0',
            description="Function decoration for backoff and retry",
            long_description=readme(),
-           py_modules=['backoff'],
+           packages=['backoff'],
            author="Bob Green",
            author_email="[email protected]",
            keywords = "backoff function decorator",