title: Cannot find module requirejs when installed globally
body: <p>I have installed <code>requirejs</code> globally, but <code>node</code> says it can't find it.</p>
  
  <pre><code># node tools/mapconv.js
  
  module.js:340
      throw err;
            ^
  Error: Cannot find module 'requirejs'
      ...
  
  # cat mapconv.js
  var requirejs = require('requirejs');
  ...
  </code></pre>
  
  <p>The module is definitely installed:</p>
  
  <pre><code># npm ls -g | grep requirejs
  ├── requirejs@2.1.6
  </code></pre>
  
  <p>I have cleared the NPM cache, but no change. Has anyone else run into this?</p>