Decommission AppVeyor

Author: Jed Mao

.npmignore

@@ -5,7 +5,6 @@
 .vscode/
 coverage/
 src/
-appveyor.yml
 circle.yml
 jsconfig.json
 tsconfig.json

README.md

@@ -6,9 +6,9 @@
 
 [![NPM version](http://img.shields.io/npm/v/postcss-nested-props.svg?style=flat)](https://www.npmjs.org/package/postcss-nested-props)
 [![npm license](http://img.shields.io/npm/l/postcss-nested-props.svg?style=flat-square)](https://www.npmjs.org/package/postcss-nested-props)
-[![Travis Build Status](https://img.shields.io/travis/jedmao/postcss-nested-props.svg?label=unix)](https://travis-ci.org/jedmao/postcss-nested-props)
-[![AppVeyor Build Status](https://img.shields.io/appveyor/ci/jedmao/postcss-nested-props.svg?label=windows)](https://ci.appveyor.com/project/jedmao/postcss-nested-props)
+[![Travis Build Status](https://img.shields.io/travis/jedmao/postcss-nested-props.svg)](https://travis-ci.org/jedmao/postcss-nested-props)
 [![codecov](https://codecov.io/gh/jedmao/postcss-nested-props/branch/master/graph/badge.svg)](https://codecov.io/gh/jedmao/postcss-nested-props)
+[![CircleCI](https://circleci.com/gh/jedmao/postcss-nested-props.svg?style=svg)](https://circleci.com/gh/jedmao/postcss-nested-props)
 
 [![npm](https://nodei.co/npm/postcss-nested-props.svg?downloads=true)](https://nodei.co/npm/postcss-nested-props/)