title: Node can't find dependency after npm install
body: <p>I am new to Node.js and hitting this problem on my DigitalOcean VPS, where my web app (Ghost) complains it can't find specific modules even after I install it:</p>
  
  <pre><code>root@3fen:/var/www/ghost# sudo npm install -g ghost-gql
  ghost-gql@0.0.2 /usr/local/lib/node_modules/ghost-gql
  └── lodash@3.10.1
  
  root@3fen:/var/www/ghost# node index.js
  ERROR: Ghost is unable to start due to missing dependencies:
    Cannot find module 'ghost-gql'
    Cannot find module 'jsonpath'
  
  Please run `npm install --production` and try starting Ghost again.
  Help and documentation can be found at http://support.ghost.org.
  </code></pre>
  
  <p>I confirmed that both entries exist in <code>package.json</code>'s dependencies block, and I also tried <code>npm install --production</code>, it executes silently and still get the same error.</p>
  
  <p>Please point me if I am missing anything in the above steps. Thank you!</p>