Moved from Atom to RSS2.0 feed

Mostly this change is so the URL can be pretty, now it'll display at
http://yoursite.com/feed and will work when minifying the site compared
to when it was at /feed/.

app/templates/app/_includes/head.html

@@ -17,5 +17,5 @@
   <link rel="shortcut icon" href="/assets/favicon.ico">
 
   <!-- RSS -->
-  <link rel="alternate" type="application/rss+xml" title="{{ site.title }} RSS" href="/feed/">
+  <link rel="alternate" type="application/rss+xml" title="{{ site.title }} RSS" href="/feed">
 </head>

app/templates/app/feed.xml

@@ -0,0 +1,33 @@
+---
+layout: null
+regenerate: true
+permalink: /feed
+---
+<?xml version="1.0" encoding="UTF-8"?>
+<rss
+  xmlns:dc="http://purl.org/dc/elements/1.1/"
+  xmlns:content="http://purl.org/rss/1.0/modules/content/"
+  xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
+  <channel>
+    <title><![CDATA[{{ site.title }}]]></title>
+    <description><![CDATA[{{ site.description }}]]></description>
+    <link>{{ site.url }}</link>
+    <generator>Jekyll</generator>
+    <lastBuildDate>{{ site.time | date_to_rfc822 }}</lastBuildDate>
+    <atom:link href="{{ site.url }}/feed/" rel="self" type="application/rss+xml"/>
+    {% for post in site.posts limit:10 %}
+    <item>
+      <title><![CDATA[{{ post.title }}]]></title>
+      {% if post.excerpt %}
+      <description><![CDATA[{{ post.excerpt }}]]></description>
+      {% else %}
+      <description><![CDATA[{{ post.content }}]]></description>
+      {% endif %}
+      <dc:creator><![CDATA[{{ site.author.name }}]]></dc:creator>
+      <pubDate>{{ post.date | date_to_rfc822 }}</pubDate>
+      <link>{{ site.url }}{{ post.url }}</link>
+      <guid isPermaLink="true">{{ site.url }}{{ post.url }}</guid>
+    </item>
+    {% endfor %}
+  </channel>
+</rss>

app/templates/app/index.html

@@ -17,5 +17,5 @@ <h2>
     {% endfor %}
   </ul>
 
-  <p class="rss-subscribe">subscribe <a href="{{ "/feed/" }}">via RSS</a></p>
+  <p class="rss-subscribe">subscribe <a href="{{ "/feed" }}">via RSS</a></p>
 </div>