title: create-react-app build doen't work in sub directory path
body: <p>create-react-app build is not working in subdirectory on web server.
  I’ve used express node web server. ‘create-react-app build’ is working on root directory.But, It doesn’t work on subdirectory.</p>
  
  <p>For example,</p>
  
  <p>localhost/ - It works.
  localhost/react-app/ - It doesn’t work.</p>
  
  <p>load related files normally. There are no errors and warnings.
  It's look like blank page. Surely I configured ‘homepage field’ in package.json.
  I don’t know why this situation occur.
  The followings are my configuration.</p>
  
  <ol>
  <li><p>set express for react  </p>
  
  <p>app.get('/*',function(req,res){
    res.sendFile(path.resolve(config.static_root+'/react-app', 'index.html'));
  });</p></li>
  <li><p>add homepage field to package.json  </p>
  
  <p>"homepage": "localhost/react-app" </p></li>
  <li><p>npm run build</p></li>
  <li><p>copy files form build folder and move to /react-app folder.</p></li>
  </ol>