Use django's `smart_text` for unicoding

Add a unicode based test for user-agent as well
Enable admin site for example purposes
use log.exception and format string
Revamp dashboard page a bit
Update tests for form
A bit more cleanup

- Add TRACK_PAGEVIEWS to example settings
Remove unused module
Use `firstof` from future
Add some tests around the managers
Test post-logout signal handling
Ignore some lines from coverage report
Remove unused tracked_dates method
Change `start_date` and `end_date` to `start_time` and `end_time`

- dates are hard to comprehend with timezone-awareness, so I generally like
  to avoid them and go with full datetimes and timedeltas
Make views time-centric, not date-centric
Bump default range to 7 previous days
A touch of backward compatibility on the form fields
Small changes to the README

- I've added a start/end datetime picker to the dashboard and commented as
  such in the README (should fix #28)
Change manager param names back to preserve backward-compat
Fix unicode case for 3.2
Move south-based migrations to south_migrations

- Per the libraries/third-party apps section of [1]

[1]: https://docs.djangoproject.com/en/1.7/topics/migrations/#upgrading-from-south