fix(docs): point to CDN bootstrap theme in docs

Author: Ryan A. Johnson

source/_templates/partials/head.njk

@@ -12,7 +12,7 @@
     integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u"
     crossorigin="anonymous">
 
-  <link rel="stylesheet" href="bootstrap.helix.css">
+  <link rel="stylesheet" href="https://2d2bf231b82dfe76fe36-fa12562cfe810d69bedcc36a0ac289ef.ssl.cf1.rackcdn.com/css/bootstrap.helix.css">
   <link rel="stylesheet" href="helix-ui.css">
   <link rel="stylesheet" href="docs.css">