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/using-illuminate-collections-outside-laravel.md

@@ -11,15 +11,17 @@ video:
 tags: [nomad-php, lightning-talk, laravel, collections]
 type: Lightning talk
 events:
-  - name: Nomad PHP
+  -
+    name: PHP South Wales
+    location: Cardiff, UK
+    url: https://www.phpsouthwales.uk
+    date: 2018-08-28
+  -
+    name: Nomad PHP
     url: https://nomadphp.com
     online: true
     date: 2017-12-21
     time: 19:00 CET
-  - name: PHP South Wales
-    location: Cardiff, UK
-    url: https://www.phpsouthwales.uk
-    date: 2018-08-28
 ---
 
 Laravel's Illuminate Collections are a powerful object-orientated way of interacting with PHP arrays, but did you know that they can be used outside of Laravel, in any PHP project?