code: function download(url, dest, cb) {
    var reportError = function(err) {
      cb(['Cannot download "', url, '": ',
        typeof err.message === 'string' ? err.message : err].join(''));
    };
    var successful = function(response) {
      return response.statusCode >= 200 && response.statusCode < 300;
    };
  
    applyProxy({ rejectUnauthorized: false }, function(options) {
      options.headers = {
        'User-Agent': [
          'node/', process.version, ' ',
          'node-sass-installer/', pkg.version
        ].join('')
      };
      try {
        request(url, options, function(err, response) {
          if (err) {
            reportError(err);
          } else if (!successful(response)) {
              reportError(['HTTP error', response.statusCode, response.statusMessage].join(' '));
          } else {
              cb();
          }
        }).on('response', function(response) {
            if (successful(response)) {
              response.pipe(fs.createWriteStream(dest));
            }
        });
      } catch (err) {
        cb(err);
      }
    });
  }
docs: Download file, if succeeds save, if not delete
  
  @param {String} url
  @param {String} dest
  @param {Function} cb
  @api private