Add support for `serve-favicon` on Windows

[styfle]

trafficstars

The following integration test currently fails to return anything on Windows but works fine on Linux and macOS.

(This snippet was taken from loopback.js)

var favicon = require('serve-favicon');
var path = require('path');

module.exports = function(icon, options) {
  icon = icon || path.join(__dirname, '../../favicon.ico');
  return favicon(icon, options);
};