Remove appveyor.yml

I don't think we will use it in future.

appveyor.yml

@@ -1,28 +0,0 @@
-# appveyor file
-# http://www.appveyor.com/docs/appveyor-yml
-version: "{build}"
-
-init:
-  - git config --global core.autocrlf input
-
-environment:
-  matrix:
-    - nodejs_version: 0.10
-
-platform:
-  - x86
-
-install:
-  - ps: Install-Product node $env:nodejs_version
-  - cmd: SET PATH=C:\Program Files (x86)\MSBuild\12.0\bin\;%PATH%
-  - cmd: SET PATH=C:\python27;%PATH%
-  - cmd: python script/bootstrap.py
-  - cmd: python script/build.py -c Debug
-
-test_script:
-  - node --version
-  - npm --version
-  - cmd: python script/cpplint.py
-  - cmd: python script/coffeelint.py
-
-build: off