Django: Use Test Database, as well as LiveServerTestCase for 1.4+  server

Hi there,

This pull addresses two related issues:

- Using a test database for all tests, set up using `DjangoTestSuiteRunner`
- For django 1.4+, using the LiveServerTestCase server instead of spinning up our own.

It also fixes a bug:

- `./manage.py harvest`'s exit code was previously the status of the server shutdown. The code indicates (and it's desirable) if it's in fact the result of all the tests passing.

This pull fixes #73 .  

Thanks!
-Steven