Replace stu auth page css to dandu css.

replace-css.js

n = document.getElementsByTagName('link').length;
for(i = 0; i < n; ++i)
  document.getElementsByTagName('link')[0].remove();
cssChild = document.createElement('link');
cssChild.type = 'text/css';
cssChild.rel = 'stylesheet';
cssChild.href = 'http://stu.fudan.edu.cn/dandu/css/dandu-style.css';
document.getElementsByTagName('head')[0].appendChild(cssChild);