code: function (file, content, charset, callback) {
      try {
          if (!file) {
              return;
          }
          charset = (charset || 'utf-8').toLowerCase();
          if (charset !== 'utf-8') {
              content = require('iconv-lite').encode(content + '\r\n', charset);
          }
          callback.call(this, file, content);
      } catch (ex) {
          throw util.format('cant write file [%s]%s for %s', charset, file, ex);
      }
  }
docs: write content to file
  @param  {string} file    - absolute file path
  @param  {string} content - file content
  @param  {string} charset - content charset, default is utf-8
  @return {undefined}