code: function bufferContents(file, enc, cb) {
      // ignore empty files
      if (file.isNull()) {
        return cb();
      }
  
      // no streams
      if (file.isStream()) {
        this.emit('error', new PluginError('gulp-livingcss', 'Streaming not supported'));
        return cb();
      }
  
      files.push(file.path);
  
      cb();
    }
docs: Buffer all files before parsing them to livingcss.