Prepend some pre-release notes

docs/topics/3.0-announcement.md

-**THIS DOCUMENT IS CURRENTLY A WORK IN PROGRESS**
+## Pre-release notes:
 
-See the [Version 3.0 GitHub issue](https://github.com/tomchristie/django-rest-framework/pull/1800) for more details.
+The 3.0 release is now ready for some tentative testing and upgrades for super keen early adopters. You can install the development version directly from GitHub like so:
+
+    pip install https://github.com/tomchristie/django-rest-framework/archive/version-3.0.zip
+
+See the [Version 3.0 GitHub issue](https://github.com/tomchristie/django-rest-framework/pull/1800) for more details on remaining work.
 
 The most notable outstanding issues still to resolved on the `version-3.0` branch are as follows:
 
@@ -12,6 +16,12 @@ The most notable outstanding issues still to resolved on the `version-3.0` branc
 * `.validate()` method on fields.
 * `.transform_<field>()` method on serializers.
 
+**Your feedback on the upgrade process and 3.0 changes is hugely important!**
+
+Please do get in touch via twitter, IRC, a GitHub ticket, or the discussion group.
+
+---
+
 # REST framework 3.0
 
 The 3.0 release of Django REST framework is the result of almost four years of iteration and refinement. It comprehensively addresses some of the previous remaining design issues in serializers, fields and the generic views.