title: Tell npm to look for node_modules inside a different dir
body: <p><code>npm</code> looks for <code>node_modules</code> in the current directory, and all its parent directories, then looks in the global location. My current proposed dir structure is:</p>
  
  <ul>
  <li>global
  <ul>
  <li>package.json</li>
  <li>node_modules/</li>
  </ul></li>
  <li>project-1
  <ul>
  <li>gulpfile.coffee</li>
  </ul></li>
  <li>project-2
  <ul>
  <li>gulpfile.coffee</li>
  </ul></li>
  </ul>
  
  <p>But this isn't where <code>npm</code> normally looks for this. Is there an environment variable I can set to deal with this, or a way I can tell it to look in a specific directory? Thanks!</p>