Remove classifier for python 3.4 and add 3.8

Author: kotfu

setup.py

@@ -38,10 +38,10 @@
         'Topic :: Software Development :: Libraries :: Python Modules',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: MIT License',
-        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
     ],
 
     # dependencies for development and testing