chore(setup.py): synchronise trove classifiers with tested versions (#222)

Author: D3X

setup.py

@@ -44,12 +44,10 @@
           'Programming Language :: Python :: 2',
           'Programming Language :: Python :: 2.7',
           'Programming Language :: Python :: 3',
-          'Programming Language :: Python :: 3.1',
-          'Programming Language :: Python :: 3.2',
-          'Programming Language :: Python :: 3.3',
-          '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',
+          'Programming Language :: Python :: 3.9',
           'Topic :: Software Development',
           'Topic :: Software Development :: Libraries :: Python Modules',
           'Topic :: Software Development :: Quality Assurance',