Fix OS classifier

Author: willingc

setup.py

@@ -79,7 +79,7 @@ def run(self):
         'Intended Audience :: System Administrators',
         'Intended Audience :: Science/Research',
         'License :: OSI Approved :: BSD License',
-        'Operating System :: Independent',
+        'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 3',