Add retro_static template tag

Unfortunately {% static %} cannot interpret any context variables passed
into it, so we need to customize things in order to use it here since
our resources are sorted by year.

Signed-off-by: Dan McGee <dan@archlinux.org>

retro/templatetags/retro.py

@@ -0,0 +1,13 @@
+from django import template
+from django.contrib.staticfiles.storage import staticfiles_storage
+
+register = template.Library()
+
+
+@register.simple_tag
+def retro_static(year, path):
+    """Like the built-in {% static %} tag but with a little extra magic."""
+    full_path = "%s/%s" % (year, path)
+    return staticfiles_storage.url(full_path)
+
+# vim: set ts=4 sw=4 et: