Add OPTIONS capability to db url parsing.

In https://github.com/santtu/dj-database-url/commit/1f8a199f8066a159eeb8d8f220f9c15d3a1e40a0 I've added capability to specify Django DB config OPTIONS via a query parameter, e.g.

```
DATABASE_URL='sqlite:///...?OPTIONS={"timeout":30}'
```

should now work. I used JSON decoding as some of the potential OPTIONS fields are string values and some are numeric values, so doing the alternative of `sqlite:///...?timeout=30` would require knowing which parameters are numeric and which are not.

The other commit is just minor cleanups to get `python setup.py test` to work, as is common with setuptools.