title: Phoenix umbrella app not hot-reloading code
body: <p>I have trouble with code reload in my Phoenix umbrella app.</p>
  
  <p>My umbrella is composed of 2 applications : app and app_web. Any change in app_web is hot reloaded as wanted, but I can’t make the same thing work with code in app.</p>
  
  <p>Where should I start looking?</p>