use Travis CI Windows build instead of AppVeyor

https://docs.travis-ci.com/user/reference/windows/

.travis.yml

@@ -2,4 +2,8 @@ branches:
   except: /^v\d/
 language: node_js
 node_js: node
-after_script: node_modules/.bin/nyc report | npx coveralls
+matrix:
+  include:
+  - after_script: node_modules/.bin/nyc report | npx coveralls
+  - os: windows
+    script: node test.js

README.md

@@ -2,7 +2,6 @@
 
 [![npm version](https://img.shields.io/npm/v/dl-tar.svg)](https://www.npmjs.com/package/dl-tar)
 [![Build Status](https://travis-ci.org/shinnn/dl-tar.svg?branch=master)](https://travis-ci.org/shinnn/dl-tar)
-[![Build status](https://ci.appveyor.com/api/projects/status/83sbr9dtbp3hreoy/branch/master?svg=true)](https://ci.appveyor.com/project/ShinnosukeWatanabe/dl-tar/branch/master)
 [![Coverage Status](https://img.shields.io/coveralls/shinnn/dl-tar.svg)](https://coveralls.io/github/shinnn/dl-tar?branch=master)
 
 A [Node.js](https://nodejs.org/) module to download and extract a [tar](https://www.gnu.org/software/tar/) archive with the [Observable](https://tc39.github.io/proposal-observable/) API