Remove python 3.3 as pymssql doesn't support it anymore (web2py#560)

See:
https://groups.google.com/forum/#!topic/pymssql/w-r8lt23KNw

Author: leonelcamara

appveyor.yml

@@ -9,10 +9,6 @@ environment:
       adapter: "mssql"
     - PYTHON: "C:/Python27"
       adapter: "mssqln"
-    - PYTHON: "C:/Python33"
-      adapter: "mssql"
-    - PYTHON: "C:/Python33"
-      adapter: "mssqln"
     - PYTHON: "C:/Python34"
       adapter: "mssql"
     - PYTHON: "C:/Python34"