Newer version of the Django docs

The 1.3 version previously linked to has a big warning that it's an insecure deprecated version and there have probably been many improvements to the docs since 1.3, so I've changed the link to 1.6, the latest stable release.
Add read the docs.

Read the docs hosts many projects using a Sphinx backend and is definitely worthy of being in the list.
Merge pull request #89 from stephenpaulger/master

Update Django doc link and add read the docs. Thanks, Stephen.