fix 404 permalink and link in intro post

404.html

@@ -1,6 +1,7 @@
 ---
 layout: default
 title: "404: Page not found"
+permalink: 404.html
 ---
 
 <div class="page">

_posts/2014-01-02-introducing-poole.md

@@ -20,7 +20,7 @@ Learn more and contribute on [GitHub](https://github.com/poole).
 
 Poole is a streamlined Jekyll site designed and built as a foundation for building more meaningful themes. Poole, and every theme built on it, includes the following:
 
-* Complete Jekyll setup included (layouts, config, [404](/404), [RSS feed](/atom.xml), posts, and [example page](/about))
+* Complete Jekyll setup included (layouts, config, [404](/404.html), [RSS feed](/atom.xml), posts, and [example page](/about))
 * Mobile friendly design and development
 * Easily scalable text and component sizing with `rem` units in the CSS
 * Support for a wide gamut of HTML elements