fix missing datadog

Author: anandkumarpatel

lib/express-app.js

@@ -7,6 +7,7 @@ var envIs = require('101/env-is');
 var passport = require('middlewares/passport');
 var compression = require('compression');
 var pkg = require('../package.json');
+var dogstatsd = require('models/datadog');
 var app = module.exports = express();
 
 if (envIs('production')) {