add 404 page

Author: aghreed

src/pages/404.js

@@ -0,0 +1,11 @@
+import React from 'react'
+import Layout from '../components/layout'
+
+const NotFoundPage = () => (
+  <Layout>
+    <h1>404: Not Found</h1>
+    <p>You just hit a route that doesn&#39;t exist... the sadness.</p>
+  </Layout>
+)
+
+export default NotFoundPage