Update Tox and Travis configurations

tox.ini

@@ -1,21 +1,20 @@
 [tox]
-envlist = py{27,34,35,36,37,38,39,310,3-win}
+envlist = py{27,34,35,36,37,38,39,310}
 skip_missing_interpreters = True
 
 [testenv]
-platform = linux
+deps =
+    flake8
+    pytest
+    pywin32; sys_platform == 'win32'
 commands =
-    python setup.py test --test-suite tests.TestSuite
-
-[testenv:py3-win]
-platform = win
-commands =
-    python -m pip install pywin32
-    python setup.py test --test-suite tests.TestSuite
+    flake8
+    pytest
 
 [testenv:py27]
 deps =
     configparser
+    {[testenv]deps}
 
 [flake8]
 exclude = .tox,env,build