title: yeoman: automatically install npm modules
body: <p>I've created a yeoman generator.</p>
  
  <p>Once I've created a project scaffold using my generator, I run the command "npm install grunt-contrib-watch grunt-contrib-connect"</p>
  
  <p>I've been following the doc here: <a href="http://yeoman.io/generators.html" rel="nofollow">http://yeoman.io/generators.html</a></p>
  
  <p>It seems to indicate that npm dependencies can be installed automatically. But I can't quiet figure out how to make this happen.</p>
  
  <p>So, how do I define npm depencies in my generator, so that the node modules get installed automatically when the scaffold gets created?</p>