title: Shopify's 'slate' package not running after installation
body: <p><strong>I just installed Shopify's 'Slate' package using npm.</strong> </p>
  
  <p>Terminal shows that the package was added to '/.npm-packages/lib'.
  <a href="https://i.stack.imgur.com/eRk5q.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eRk5q.png" alt="enter image description here"></a>
  However, when I attempt to build a new shopify theme using the command 'slate theme newthemename', the command isn't found...
  <a href="https://i.stack.imgur.com/1isEr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1isEr.png" alt="enter image description here"></a>
  ...even though slate clearly <em>was</em> installed.
  <a href="https://i.stack.imgur.com/kRxP1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kRxP1.png" alt="enter image description here"></a></p>
  
  <p>Curious to figure out what I'm doing wrong, so any help/advice is much appreciated!</p>