Kill AppVeyor builds.

We'll move to CircleCI when we find an active maintainer who wants to push new releases.

appveyor.yml

@@ -1,58 +0,0 @@
-# version format
-version: 1.0.{build}
-
-environment:
-  matrix:
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      PYTHON: "C:\\Python36-x64"
-  FBXSDK_SDKS: sdk
-
-stack: python %PYTHON%
-
-#temporarily disabled
-#cache:
-#  - C:\Users\appveyor\.conan\data -> appveyor.yml, conanfile.py
-
-init:
-  - git config --global filter.lfs.required false
-  - git config --global filter.lfs.smudge "git-lfs smudge --skip %f"
-  - git config --global filter.lfs.process "git-lfs filter-process --skip"
-
-install:
-  - cinst zstandard
-  - ps: Start-FileDownload 'https://github.com/zellski/FBXSDK-Windows/archive/2019.2.tar.gz'
-  - 7z e 2019.2.tar.gz
-  - 7z x 2019.2.tar
-  - ps: move -v .\FBXSDK-Windows-2019.2\sdk\ .
-  - ps: zstd -d -r --rm sdk
-  - cmd: echo "Downloading conan..."
-  - cmd: set PATH=%PYTHON%;%PYTHON%\Scripts;%PATH%
-  - cmd: python --version
-  - cmd: python -m pip install --upgrade pip
-  - cmd: pip install conan
-  - cmd: conan user # Create the conan data directory
-  - cmd: conan remote add bincrafters https://api.bintray.com/conan/bincrafters/public-conan
-  - cmd: conan --version
-
-build_script:
-  - cmd: conan install . -i build -s build_type=Release -s compiler="Visual Studio" -s compiler.version=15
-  - cmd: conan build -bf build .
-  - cmd: move build\Release\FBX2glTF.exe build\Release\FBX2glTF-windows-x64.exe
-
-test: off
-
-artifacts:
-  - path: build/Release/FBX2glTF-windows-x64.exe
-
-deploy:
-  tag: $(APPVEYOR_REPO_TAG_NAME)
-  description: ''
-  provider: GitHub
-  auth_token:
-    secure: OSvhQP0O9uaH+OFOJpbGiiBMRTOJ+H/VJHqVBhq39RNDnOfUEr/yjJNKh3JSdNqj
-  artifact: build/Release/FBX2glTF-windows-x64.exe
-  draft: true
-  prerelease: true
-  on:
-    branch: master
-    APPVEYOR_REPO_TAG: true