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-8-module-development.md

@@ -20,7 +20,8 @@ meta:
       height: 540
       width: 960
 events:
-  - name: DrupalCamp London 2016
+  -
+    name: DrupalCamp London 2016
     location: London, UK
     date: 2016-03-05
 ---