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-rejoining-the-herd.md

@@ -7,7 +7,8 @@ speakerdeck:
   ratio: "1.37081659973226"
   url: https://speakerdeck.com/opdavies/drupal-rejoining-the-herd
 events:
-  - name: PHP South Coast 2016
+  -
+    name: PHP South Coast 2016
     location: Portsmouth, UK
     url: http://2016.phpsouthcoast.co.uk
     date: 2016-06-11