Jekyll doesn't like layouts starting with a number.

Change-Id: I8b5e6d8905b447b823df91d2f497bbb90b5fa8da
diff --git a/404.md b/404.md
index fce6c7e..00c75eb 100644
--- a/404.md
+++ b/404.md
@@ -1,5 +1,5 @@
 ---
-layout: 404
+layout: notfound
 title: Not Found
 exclude: true
 permalink: /404.html
diff --git a/_layouts/404.html b/_layouts/notfound.html
similarity index 100%
rename from _layouts/404.html
rename to _layouts/notfound.html