Switch to a single site feed covering all post categories

This changes the existing `index.xml` feed to include all posts to the
site regardless of category. This also removes the `blog.xml` feed, as
that only covered one category that is mostly unused.

Fixes #1467
Fixes #849

Author: jryans

_includes/headertop.html

@@ -56,5 +56,4 @@
     <script type="text/javascript">try{Typekit.load();}catch(e){}</script> -->
 
     <!-- Atom feeds -->
-    <link rel="alternate" type="application/atom+xml" title="News Feed" href="{{ site.baseurl }}/feed/index.xml" />
-    <link rel="alternate" type="application/atom+xml" title="Blog Feed" href="{{ site.baseurl }}/feed/blog.xml" />
+    <link rel="alternate" type="application/atom+xml" title="Feed" href="{{ site.baseurl }}/feed/index.xml" />

feed/blog.xml

@@ -3,7 +3,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom">
   <id>https://www.scala-lang.org/</id>
-  <title type="text" xml:lang="en">{{ site.title }} :: News</title>
+  <title type="text" xml:lang="en">{{ site.title }}</title>
   <link type="application/atom+xml" href="https://www.scala-lang.org/feed/index.xml" rel="self"/>
   <link type="text/html" href="https://www.scala-lang.org/news/" rel="alternate"/>
 
@@ -13,7 +13,7 @@
   </author>
   <rights>Copyright (c) 2002-{{ site.time | date:"%Y" }} École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland</rights>
 
-  {% for post in site.categories.news limit:20 %}
+  {% for post in site.posts limit:20 %}
   <entry>
     <title>{{ post.title }}</title>
     <link href="https://www.scala-lang.org{{ post.url }}"/>