Release notes for 0.2.

[lovelydinosaur]

Port an existing API to 0.2 (once it's almost ready to go) using the notes in: https://groups.google.com/d/topic/django-rest-framework/2axB7NjXD8Y/discussion

Compile a simple, definitive list of all the changes, so it's not a total PITA for users to upgrade.

This is pending some final bits of work in the bitbucket -dev fork.