title: UserScript - How can I know one user has installed the Tampermonkey or not?
body: <p>I develop a UserScript and wrote a document for how install it. I found the procedure is too hard for user, so I willing make a script in website to install them automatically.</p>
  
  <p>My plan:</p>
  
  <ul>
  <li>Get browser info from user and open the Tampermonkey extention page(chrome webstore or AMO)</li>
  <li>When the Tampermonkey had installed, open a page whick URL ends with '.user.js'</li>
  </ul>
  
  <p>The problem is how can I get "When the Tampermonkey had installed"?</p>