message: fixed(demo): now should use bs4 alfa.6
diff: @@ -8,7 +8,7 @@ const files = {
  const toReplace = [
  {
  from: '<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">',
  - to: `<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.5/css/bootstrap.min.css" rel="stylesheet">
  + to: `<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet">
  <link rel="stylesheet" href="assets/css/glyphicons.css">`
  }, {
  from: '<script src="assets/js/prettify.min.js"></script>',
  