Upgrade express to 4.x

See https://travis-ci.org/oaeproject/Hilary/builds/20117955

``` 
1) "before all" hook
  0 passing (2s)
  1 failing
  1)  "before all" hook:
     Uncaught TypeError: Object function createApplication() {
  var app = function(req, res, next) {
    app.handle(req, res, next);
  };
  mixin(app, proto);
  mixin(app, EventEmitter.prototype);
  app.request = { __proto__: req, app: app };
  app.response = { __proto__: res, app: app };
  app.init();
  return app;
} has no method 'cookieParser'
      at Object.module.exports.setupServer (/home/travis/build/oaeproject/Hilary/node_modules/oae-util/lib/server.js:9:1403)
      at Object.module.exports.init (/home/travis/build/oaeproject/Hilary/node_modules/oae-util/lib/oae.js:9:1791)
      at /home/travis/build/oaeproject/Hilary/node_modules/oae-tests/runner/beforeTests.js:9:9977
      at /home/travis/build/oaeproject/Hilary/node_modules/oae-util/lib/redis.js:9:3127
      at b (domain.js:183:18)
      at b (domain.js:183:18)
      at try_callback (/home/travis/build/oaeproject/Hilary/node_modules/redis/index.js:573:9)
      at RedisClient.return_reply (/home/travis/build/oaeproject/Hilary/node_modules/redis/index.js:661:13)
      at ReplyParser.<anonymous> (/home/travis/build/oaeproject/Hilary/node_modules/redis/index.js:309:14)
      at ReplyParser.EventEmitter.emit (events.js:95:17)
```