title: Use Grunt to start Express server
body: <p>I would like to add a task to my Gruntfile in order to start my Express server instead of the default server. 
  I tried to had a task and require("server.js") but I think this isn't the right way to do that: running "grunt mytask" there are no errors but the command return immediately..and the express server isn't listening
  Thank you for your help !</p>