Allow use of native migrations in 1.7
Added (first pass) notes to docs & release notes. Backed out `SOUTH_MIGRATION_MODULES` setting from `rest_framework.settings`
Merge branch '2.4.0' of github.com:tomchristie/django-rest-framework into #1559

Conflicts:
	docs/topics/release-notes.md
Updated docs for South v1.0
Alter other reference to migrations.
Improve wording.
Merge pull request #1654 from carltongibson/1559-take-2

Allow use of native migrations in 1.7 — Take 2