Add REST framework: Under the hood. video to the 3.0 announcement.

Author: tomchristie

docs/topics/3.0-announcement.md

@@ -28,10 +28,18 @@ Notable features of this new release include:
 
 Significant new functionality continues to be planned for the 3.1 and 3.2 releases. These releases will correspond to the two [Kickstarter stretch goals](https://www.kickstarter.com/projects/tomchristie/django-rest-framework-3) - "Feature improvements" and "Admin interface". Further 3.x releases will present simple upgrades, without the same level of fundamental API changes necessary for the 3.0 release.
 
-Below is an in-depth guide to the API changes and migration notes for 3.0.
+---
+
+#### REST framework: Under the hood.
+
+This talk from the Django: Under the Hood event in Amsterdam, Nov 2014 gives some good background context on the design decisions behind 3.0.
+
+<iframe width="560" height="315" src="//www.youtube.com/embed/3cSsbe-tA0E" frameborder="0" allowfullscreen></iframe>
 
 ---
 
+*Below is an in-depth guide to the API changes and migration notes for 3.0.*
+
 ## Request objects
 
 #### The `.data` and `.query_params` properties.