code: function addExampleFiles(options) {
  
  
    return new Promise(function(resolve, reject) {
      var templateFile = path.join(__dirname, '../template/cli.html');
      var tasks = [];
  
      tasks.push(writeHTMLFile(options));
      // add necessary JS files
      tasks.push(copyFileToDir('specificity-graph-standalone.js', options.directory))
      tasks.push(copyFileToDir('example.js', options.directory));
  
      // make sure all these aync tasks are done.
      Promise.all(tasks).then(resolve,reject);
    });
  }
docs: This method copy the required js/css files and also
  inject json into html.
  @param  {Object}  options            Options data
  @param  {String}  options.directory  Directory
  @param  {Object}  options.json       JSON data.
  @return {void}