code: function (cb) {
      // check if we have a custom index file set
      if (settings.index) {
        // generate the real index file path
        var indexFile = process.cwd() + '/' + settings.index;
  
        // check if the file exists, throw an error otherwise
        if (!grunt.file.exists(indexFile)) {
          grunt.log.error('Index file: "' + indexFile + '" not found');
          cb('Index file: "' + indexFile + '" not found');
          return;
        }
  
        // load the file contents
        sourceFile = grunt.file.read(indexFile);
      }
  
      // modify the sourcefile css according to the settings
      var css = settings.css.map(function (file) {   
        if (settings.snapshot && file.search('http://') !== -1) {
          return '<link rel="stylesheet" type="text/css" href="' + path.basename(file) + '"/>';
        } else {
          return '<link rel="stylesheet" type="text/css" href="' + file + '"/>';
        }
      });
      sourceFile = sourceFile.replace('{{css}}', css.join(''));
  
      // spit out the default sourcefile
      cb(sourceFile);
    }
docs: gets the user defined source file, or uses the default one