title: ng serve throws node_modules appears empty error
body: <p>I just started learning Angular 4, and as part of learning process i did the following:</p>
  
  <p>Install <code>Node.js (version 8)</code>.</p>
  
  <p>Ran this command <code>npm install -g @angular/cli</code></p>
  
  <p>created a new project through CLI: <code>ng new my-first-app</code></p>
  
  <p>As soon as i ran this command: <code>ng serve</code>, i got an error <code>node_module</code> appear empty, you may need to run 'npm install'. Once i run npm install, it installed a few libraries and now <code>ng serve</code> builds and runs the project. i am trying to understand why did i need to <code>npm install</code> and what did it install? shouldn't all the prerequisites have been installed with this command <code>npm install -g @angular/cli</code></p>