Support cookie hostname rewrite

[JohnWu-Pro]

New option cookieRewrite, and sample implementation:

// Copied from https://github.com/andrewrk/node-proxy-middleware
function rewriteCookieHostname(req, res, proxyRes, options) {
  if (!(options.cookieRewrite && proxyRes.headers['set-cookie'])) {
    return;
  }

  var existingCookies = proxyRes.headers['set-cookie'],
      rewrittenCookies = [],
      rewriteHostname = (true === options.cookieRewrite) ? os.hostname() : options.cookieRewrite;

  if (!Array.isArray(existingCookies)) {
    existingCookies = [ existingCookies ];
  }

  for (var i = 0; i < existingCookies.length; i++) {
    var rewrittenCookie = existingCookies[i].replace(/(Domain)=[a-z\.-_]*?(;|$)/gi, '$1=' + rewriteHostname + '$2');

    if (!req.connection.encrypted) {
      rewrittenCookie = rewrittenCookie.replace(/;\s*?(Secure)/i, '');
    }
    rewrittenCookies.push(rewrittenCookie);
  }

  proxyRes.headers['set-cookie'] = rewrittenCookies;
}