add py3.{7,8} support

Author: chenrui333

setup.py

@@ -69,12 +69,16 @@ def get_message_catalogs():
         "Topic :: Communications :: File Sharing",
         "Topic :: Software Development :: Libraries :: Python Modules",
         "Topic :: System :: Filesystems",
+        "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",
     ],
 )

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py33,py34,py35,py36
+envlist = py27,py33,py34,py35,py36,py37,py38
 
 [testenv]
 commands = python setup.py test