fix: 修改readme，文档改为使用cnpm运行

README.md

@@ -6,16 +6,16 @@
 
 ``` bash
 # install dependencies
-npm install
+cnpm install
 
 # serve with hot reload at localhost:8080
-npm run dev
+cnpm run dev
 
 # build for production with minification
-npm run build
+cnpm run build
 
 # build for production and view the bundle analyzer report
-npm run build --report
+cnpm run build --report
 ```
 
 For detailed explanation on how things work, checkout the [guide](http://vuejs-templates.github.io/webpack/) and [docs for vue-loader](http://vuejs.github.io/vue-loader).