Restructure macros

- Split macros.html in per-edition files
- Create new snippets.html macro file with utterances snippet
- Move support.html to snippets.html as new macro
- Create new `latest_post` macro in 2nd edition macros.html

blog/templates/edition-2/index.html

@@ -1,6 +1,7 @@
 {% extends "edition-2/base.html" %}
 
-{% import "macros.html" as macros %}
+{% import "edition-2/macros.html" as macros %}
+{% import "snippets.html" as snippets %}
 
 {% block title %}{{ config.title }}{% endblock title %}
 
@@ -71,7 +72,7 @@
 
 <div class="">
     <h2>Support Me</h2>
-    {% include "support.html" %}
+    {{ snippets::support() }}
 </div>
 {% endblock main %}