Test improvements.

- use a context manager to test `_meta` model values. This replaces  `setUp()` and `tearDown()` with a more obvious mechanism.
- don't use testcase-wide models; setup the necessary models directly in the tests they are needed in.
- Foobar is a common model, so remove the duplicate code determining its template path
- in all cases the `expected` value is what it should be. Don't inconsistently coerce it into a list in the assertions.
Coverage improvements.

- don't worry about the deprecated stuff
- don't worry about the Django-version-specific stuff
- streamline an exception assertion
- don't worry about the rendered_template cache that isn't actually used during that TestCase
.gitignore update
Readme - list supported Django versions
Add CHANGES.rst
Readme and setup.py text updates.
Merge pull request #18 from joncotton/v1.3.0-prep

Finalize v1.3.0