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 --reporter=text-lcov | npx coveralls
+matrix:
+  include:
+  - after_script: node_modules/.bin/nyc report --reporter=text-lcov | npx coveralls
+  - os: windows
+    script: node test.js

README.md

@@ -2,14 +2,13 @@
 
 [![npm version](https://img.shields.io/npm/v/metalsmith-babel.svg)](https://www.npmjs.com/package/metalsmith-babel)
 [![Build Status](https://travis-ci.org/babel/metalsmith-babel.svg?branch=master)](https://travis-ci.org/babel/metalsmith-babel)
-[![Build status](https://ci.appveyor.com/api/projects/status/k49tibi2lsbl0xk2?svg=true)](https://ci.appveyor.com/project/ShinnosukeWatanabe/metalsmith-babel)
 [![Coverage Status](https://img.shields.io/coveralls/babel/metalsmith-babel.svg)](https://coveralls.io/github/babel/metalsmith-babel)
 
 [Babel](https://babeljs.io/) plugin for [Metalsmith](https://github.com/segmentio/metalsmith)
 
 ## Installation
 
-[Use](https://docs.npmjs.com/cli/install) [npm](https://docs.npmjs.com/getting-started/what-is-npm):
+[Use](https://docs.npmjs.com/cli/install) [npm](https://docs.npmjs.com/about-npm/):
 
 ```
 npm install metalsmith-babel