Update travis.yml

Author: qiubaiying

.travis.yml

@@ -2,9 +2,8 @@ language: ruby
 rvm:
   - 2.4.1
 install: 
-  - gem install jekyll html-proofer
   - gem install jekyll-paginate
-script: jekyll build && htmlproofer ./_site
+script: jekyll build
 after_success:
   - bash <(curl -s https://codecov.io/bash)