Missing rss feed link

In layouts/default.html there should be a link tag for the rss feed

```
<link rel="alternate" type="application/rss+xml" title="{{ data.title }}" href="/rss.xml" />
```

and also a link to it in the navbar (or wherever) as well

```
<li>
    <a href="/rss.xml"><img alt="rss feed" width="16px" src="/assets/media/rss-16x16.png"></a>
</li>
```
