Added Python 3.7 builds

Author: Kojoley

.appveyor.yml

@@ -3,9 +3,11 @@ environment:
     - PYTHON: "C:\\Python27"
     - PYTHON: "C:\\Python35"
     - PYTHON: "C:\\Python36"
+    - PYTHON: "C:\\Python37"
     - PYTHON: "C:\\Python27-x64"
     - PYTHON: "C:\\Python35-x64"
     - PYTHON: "C:\\Python36-x64"
+    - PYTHON: "C:\\Python37-x64"
 
 install:
   - "%PYTHON%\\python.exe -m pip install wheel"