fix classifiers on setup.cfg

Author: koxudaxi

setup.cfg

@@ -8,13 +8,13 @@ author = Koudai Aono
 author_email = koxudaxi@gmail.com
 license_file = LICENSE
 classifiers =
-        'Development Status :: 2 - Pre-Alpha'
-        'Natural Language :: English'
-        'License :: OSI Approved :: MIT License'
-        'Programming Language :: Python :: 3'
-        'Programming Language :: Python :: 3.6'
-        'Programming Language :: Python :: 3.7'
-        'Programming Language :: Python :: Implementation :: CPython'
+        Development Status :: 2 - Pre-Alpha
+        Natural Language :: English
+        License :: OSI Approved :: MIT License
+        Programming Language :: Python :: 3
+        Programming Language :: Python :: 3.6
+        Programming Language :: Python :: 3.7
+        Programming Language :: Python :: Implementation :: CPython
 
 [options]
 packages = find: