Consistent ordering and formatting for talk events

Use a consistent format for talk events, with the most recent talk at
the top of the list with the rest in a descending order.

This removes the need to use a `reverse` filter in the events partial.

source/_talks/drupal-ldap-module.md

@@ -2,7 +2,8 @@
 title: Drupal and the LDAP module
 description: A review and demonstration of some of the recent single sign-on work that I did using Drupal’s LDAP module.
 events:
-  - name: South Wales Drupal user group (SWDUG)
+  -
+    name: South Wales Drupal user group (SWDUG)
     location: Cardiff, UK
     date: 2013-07-10
 ---