Merge pull request #41 from Dunedan/404-template

Provide a template for not existing resources.

binder/templates/404.html

@@ -0,0 +1,7 @@
+{% extends "base.html" %}
+
+{% block pageheader %}Page not found{% endblock pageheader %}
+
+{% block body %}
+<p>We're sorry, but the requested page could not be found.</p>
+{% endblock %}