setup.py: Add Python 3.6-3.8 to trove classifiers

Author: tony

setup.py

@@ -24,6 +24,9 @@
         'Topic :: Software Development :: Build Tools',
         'License :: Other/Proprietary License',
         'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
     ],
     keywords='qencode, qencode.com, cloud.qencode.com',
     packages=['qencode'],