Add posts, categories, category, tags, tag, and collection layouts

Replace sample pages with hard coded HTML and Liquid in favor of a layout that does all the heavy lifting. Assign the appropriate `layout` via YAML Front Matter and away you go.

_layouts/posts.html

@@ -0,0 +1,29 @@
+---
+layout: archive
+---
+
+{{ content }}
+
+<ul class="taxonomy-index">
+  {% assign postsInYear = site.posts | group_by_exp: 'post', 'post.date | date: "%Y"' %}
+  {% for year in postsInYear %}
+    <li>
+      <a href="#{{ year.name }}">
+        <strong>{{ year.name }}</strong> <span class="taxonomy-count">{{ year.items | size }}</span>
+      </a>
+    </li>
+  {% endfor %}
+</ul>
+
+{% assign postsByYear = site.posts | group_by_exp: 'post', 'post.date | date: "%Y"' %}
+{% for year in postsByYear %}
+  <section id="{{ year.name }}" class="taxonomy-section">
+    <h2 class="archive__subtitle">{{ year.name }}</h2>
+    <div class="entries-{{ page.entries_layout | default: 'list' }}">
+      {% for post in year.items %}
+        {% include archive-single.html %}
+      {% endfor %}
+    </div>
+    <a href="#page-title" class="back-to-top">{{ site.data.text[site.locale].back_to_top | default: 'Back to Top' }} &uarr;</a>
+  </section>
+{% endfor %}