Remove appveyor.yml

This configuration isn't used anymore - appveyor setup is defined on server

appveyor.yml

@@ -1,25 +0,0 @@
-# appveyor file
-# http://www.appveyor.com/docs/appveyor-yml
-version: "{build}"
-
-os: Visual Studio 2015
-
-init:
-  - git config --global core.autocrlf input
-
-platform:
-  - x86
-  - x64
-
-install:
-  - cmd: SET PATH=C:\Program Files (x86)\MSBuild\14.0\bin\;%PATH%
-  - cmd: SET PATH=C:\python27;%PATH%
-  - cmd: python script/cibuild
-
-branches:
-  only:
-    - master
-
-# disable build and test phases
-build: off
-test: off