fix code style of setup.py

Author: Zang Zhiya

setup.py

@@ -13,7 +13,7 @@
       author_email='[email protected]',
       description='Extended JWT integration with Flask',
       long_description='Extended JWT integration with Flask',
-      keywords = ['flask', 'jwt', 'json web token'],
+      keywords=['flask', 'jwt', 'json web token'],
       packages=['flask_jwt_extended'],
       zip_safe=False,
       platforms='any',