appveyor: also test Python 3.4, 3.5, 3.6 and 3.7 (64 bit)

appveyor.yml

@@ -8,9 +8,26 @@ environment:
   matrix:
     # https://www.appveyor.com/docs/windows-images-software/#python
     - PYTHON: "C:\\Python27"
-      PYTHON_VERSION: "2.7.x" # currently 2.7.15
+      PYTHON_VERSION: "2.7.x"
       PYTHON_ARCH: "32"
 
+    - PYTHON: "C:\\Python34-x64"
+      PYTHON_VERSION: "3.4.x"
+      PYTHON_ARCH: "64"
+
+    - PYTHON: "C:\\Python35-x64"
+      PYTHON_VERSION: "3.5.x"
+      PYTHON_ARCH: "64"
+
+    - PYTHON: "C:\\Python36-x64"
+      PYTHON_VERSION: "3.6.x"
+      PYTHON_ARCH: "64"
+
+    - PYTHON: "C:\\Python37-x64"
+      PYTHON_VERSION: "3.7.x"
+      PYTHON_ARCH: "64"
+
+
 install:
   # If there is a newer build queued for the same PR, cancel this one.
   # The AppVeyor 'rollout builds' option is supposed to serve the same