Add appveyor (#112)

* Add appveyor.yml

* Add verify-travis-appveyor

* Add AppVeyor badge

* Tweak Travis badge label

* Use img.shields.io for Travis badge

README.md

@@ -7,7 +7,8 @@
 [![Sponsors on Open Collective](https://opencollective.com/level/sponsors/badge.svg)](#sponsors)
 [![npm](https://img.shields.io/npm/v/level.svg)](https://www.npmjs.com/package/level)
 ![Node version](https://img.shields.io/node/v/level.svg)
-[![Build Status](https://secure.travis-ci.org/Level/level.svg)](http://travis-ci.org/Level/level)
+[![Travis](https://img.shields.io/travis/Level/level.svg?label=travis)](http://travis-ci.org/Level/level)
+[![AppVeyor](https://img.shields.io/appveyor/ci/Level/level.svg?label=appveyor)](https://ci.appveyor.com/project/Level/level)
 [![dependencies](https://david-dm.org/Level/level.svg)](https://david-dm.org/level/level)
 [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com)
 [![npm](https://img.shields.io/npm/dm/level.svg)](https://www.npmjs.com/package/level)

appveyor.yml

@@ -0,0 +1,22 @@
+version: "{build}"
+build: off
+skip_tags: true
+
+environment:
+  matrix:
+    - nodejs_version: "6"
+    - nodejs_version: "8"
+    - nodejs_version: "9"
+    - nodejs_version: "10"
+
+platform:
+  - x86
+  - x64
+
+install:
+  - ps: Install-Product node $env:nodejs_version $env:platform
+  - set PATH=%APPDATA%\npm;%APPVEYOR_BUILD_FOLDER%\node_modules\.bin;%PATH%
+  - npm i
+
+test_script:
+  - npm test

package.json

@@ -39,10 +39,11 @@
   },
   "devDependencies": {
     "standard": "^11.0.0",
-    "tape": "^4.2.2"
+    "tape": "^4.2.2",
+    "verify-travis-appveyor": "^3.0.0"
   },
   "scripts": {
-    "test": "standard && node test.js",
+    "test": "standard && node test.js && verify-travis-appveyor",
     "postinstall": "opencollective-postinstall || exit 0"
   },
   "engines": {