Better appveyor config

.appveyor.yml

@@ -3,16 +3,21 @@ environment:
     TOXENV: "py"
 
   matrix:
-    - PYTHON: "C:\\Python36"
     - PYTHON: "C:\\Python27"
+    - PYTHON: "C:\\Python35"
+    - PYTHON: "C:\\Python36"
+
+init:
+  - SET PATH=%PYTHON%;%PATH%
+  - python -c "import sys;sys.stdout.write(sys.version)"
 
 install:
-  - "%PYTHON%\\python.exe -m pip install -U pip setuptools wheel tox"
+  - python -m pip install -U pip setuptools wheel tox
 
 build: false
 
 test_script:
-  - "%PYTHON%\\python.exe -m tox"
+  - python -m tox
 
 branches:
   only: