fix declare package_data from root

setup.py

@@ -5,8 +5,7 @@ setup(
    name='backbone-adapter-testsuite',
    packages=find_packages(),
    package_data={
-      'features': ['features/*.feature'], 
-      'fixtures': ['*.json'],
+      '': ['features/*.feature', 'fixtures/*.json'], 
    },
    include_package_data=True,
    zip_safe=False