Concatenated all JS into a single file (#624)

no issue

- moved large inline JS from templates into separate JS files
  - floating header
  - gallery card support
- use `gulp-concat` to concatenate all JS files into a single `built/casper.js` file
- reduces external JS file requests from 3 (jquery, infinite-scroll.js, jquery.fitvids.js) down to 2 (jquery, casper.js) and reduces page size by removing repeated inline code

default.hbs

@@ -55,27 +55,14 @@
     </div>
     {{/if}}
 
-    <script>
-        var images = document.querySelectorAll('.kg-gallery-image img');
-        images.forEach(function (image) {
-            var container = image.closest('.kg-gallery-image');
-            var width = image.attributes.width.value;
-            var height = image.attributes.height.value;
-            var ratio = width / height;
-            container.style.flex = ratio + ' 1 0%';
-        })
-    </script>
-
-
-    {{!-- jQuery + Fitvids, which makes all video embeds responsive --}}
+    {{!-- jQuery, required for fitvids --}}
     <script
         src="https://code.jquery.com/jquery-3.4.1.min.js"
         integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo="
         crossorigin="anonymous">
     </script>
-    <script type="text/javascript" src="{{asset "built/jquery.fitvids.js"}}"></script>
-
-    <script src="{{asset "built/infinitescroll.js"}}"></script>
+    {{!-- Fitvids (for responsive video embeds), infinite scroll, floating header, and gallery card support --}}
+    <script src="{{asset "built/casper.js"}}"></script>
 
     {{!-- The #block helper will pull in data from the #contentFor other template files. In this case, there's some JavaScript which we only want to use in post.hbs, but it needs to be included down here, after jQuery has already loaded. --}}
     {{{block "scripts"}}}