moved to github actions: remove cirrus and appveyor configs

.cirrus.yml

@@ -1,8 +0,0 @@
-osx_test_task:
-  osx_instance:
-    image: mojave-base
-  install_script: brew install erlang
-  test_script: |
-    ./bootstrap
-    ./rebar3 ct
-

README.md

@@ -1,6 +1,6 @@
 # Rebar3
 
-![Build Status](https://github.com/erlang/rebar3/workflows/Common%20Test/badge.svg) [![OSX Build Status](https://api.cirrus-ci.com/github/erlang/rebar3.svg)](https://cirrus-ci.com/github/erlang/rebar3) [![Windows Build Status](https://ci.appveyor.com/api/projects/status/yx4oitd9pvd2kab3?svg=true)](https://ci.appveyor.com/project/TristanSloughter/rebar3)
+![Build Status](https://github.com/erlang/rebar3/workflows/Common%20Test/badge.svg)
 
 1. [What is Rebar3?](#what-is-rebar3)
 2. [Why Rebar3?](#why-rebar3)

appveyor.yml

@@ -1,20 +0,0 @@
-version: "{build}"
-branches:
-  only:
-  - master
-environment:
-  matrix:
-  - erlang_vsn: 19.2
-  - erlang_vsn: 18.3
-  - erlang_vsn: 17.5
-install:
-- ps: choco install erlang --version $env:erlang_vsn
-build_script:
-- ps: cmd.exe /c 'bootstrap.bat'
-test_script:
-- ps: cmd.exe /c 'rebar3.cmd ct'
-notifications:
-- provider: GitHubPullRequest
-  on_build_success: true
-  on_build_failure: true
-  on_build_status_changed: false