Allows for standard Jekyll code highlighting with distill template (#…

…3002)

As described in #300,
standard Markdown code highlighting doesn't work in the Distill template
because it is clobbered by the Distill "Prism" syntax highlighting. This
PR will allow d-code tags (distill-specific code tags) to function with
the Distill syntax highlighter, but will default `highlight` and
Markdown code blocks to use the Jekyll/Rouge highlighter.

This PR also removes overrides.js, which is currently broken because
jquery isn't loaded.

_layouts/distill.liquid

@@ -6,7 +6,6 @@
     <!-- Distill js -->
     <script src="{{ '/assets/js/distillpub/template.v2.js' | relative_url }}"></script>
     <script src="{{ '/assets/js/distillpub/transforms.v2.js' | relative_url }}"></script>
-    <script src="{{ '/assets/js/distillpub/overrides.js' | relative_url }}"></script>
     {% if page._styles %}
       <!-- Page/Post style -->
       <style type="text/css">

_posts/2018-12-22-distill.md

@@ -131,8 +131,7 @@ For larger blocks of code, add a `block` attribute:
   }
 </d-code>
 
-**Note:** `<d-code>` blocks do not look good in the dark mode.
-You can always use the default code-highlight using the `highlight` liquid tag:
+**Note:** `<d-code>` blocks do not look good in the dark mode. You can instead use the standard Jekyll syntax highlight with the `highlight` liquid tag.
 
 {% highlight javascript %}
 var x = 25;
@@ -141,6 +140,13 @@ return x \* x;
 }
 {% endhighlight %}
 
+You can also write standard Markdown code blocks in triple ticks with a language tag, for instance:
+
+```python
+def foo(x):
+  return x
+```
+
 ---
 
 ## Interactive Plots