using yarn instead of npm

Author: BiYuqi

.travis.yml

@@ -12,12 +12,11 @@ install:
   - npm install
 
 script:
-  # 为了能在git-pages预览 单独发布带有二级域名的包
   - npm run build
 
 after_script:
   - cd ./dist
-  - git init 
+  - git init
   - git config user.name "BiYuqi"
   - git config user.email "biyuqiwan@163.com"
   - git add .
@@ -29,4 +28,4 @@ branches:
     - master
 env:
  global:
-   - GH_REF: github.com/BiYuqi/vue-intersection-observer.git
+   - GH_REF: github.com/BiYuqi/vue-intersection-observer.git