从.gitignore中删除3个动态生成的文件，方便 gh-pages 展示正常站点
Merge branch 'gh-pages' of github.com:xindong/7999.com into gh-pages

* 'gh-pages' of github.com:xindong/7999.com:
  set CNAME of 7999.xindong.com for GitHub Pages