Update appveyor config

Author: hackebrot

appveyor.yml

@@ -1,40 +1,15 @@
-# What Python version is installed where:
-# http://www.appveyor.com/docs/installed-software#python
-
 environment:
   matrix:
-    - PYTHON: "C:\\Python27-x64"
-      TOX_ENV: "py27"
-
-    - PYTHON: "C:\\Python34-x64"
-      TOX_ENV: "py34"
-
-    - PYTHON: "C:\\Python35-x64"
-      TOX_ENV: "py35"
-
+  - TOXENV: py27
+  - TOXENV: py34
+  - TOXENV: py35
+  - TOXENV: py36
+  - TOXENV: py37
 
-init:
-  - "%PYTHON%/python -V"
-  - "%PYTHON%/python -c \"import struct;print( 8 * struct.calcsize(\'P\'))\""
-  - "%PYTHON%/python -c \"import sys;print(sys.version_info[0] == 2)\""
-  - "%PYTHON%/python -c \"import platform;print(platform.system().lower().startswith(\'windows\'))\""
+build: off
 
 install:
-  - "%PYTHON%/Scripts/easy_install -U pip"
-  - "%PYTHON%/Scripts/pip install tox"
-  - "%PYTHON%/Scripts/pip install wheel"
-
-build: false  # Not a C# project, build stuff at the test step instead.
+- pip install tox
 
 test_script:
-  - "%PYTHON%/Scripts/tox -e %TOX_ENV%"
-
-after_test:
-  - "%PYTHON%/python setup.py bdist_wheel"
-  - ps: "ls dist"
-
-artifacts:
-  - path: dist\*
-
-#on_success:
-#  - TODO: upload the content of dist/*.whl to a public wheelhouse
+- tox