Annual Owning a Home API county-limit update

[higs4281]

At the end of every year, the owning-a-home API's county-limit values
need to be updated. This PR adds data files and an updated fixture
that will load the new limits.

After the OaH API repo is updated and re-imported into cfgov-refresh,
the limit records can be updated in any environment's database with
this manage.py command:

load_county_limits --confirm=y

The update process is documented at [GHE]/OAH/OAH-notes/wiki/Periodic-data-load-procedures.

Regarding Travisty and atonement

This PR also atones for some sins.

• It removes that nasty initial_data fixture that loaded 6,524 objects with every deploy
• It drops a convoluted csvkit dependency
• It fixes a test-killer that was hiding in the views.py file

This repo was plagued by mysterious Travis test failures that didn't happen locally, and it turns out it was my doing.
In responding to a security issue about the API's use of unvalidated query strings, I added a whitelist of state values, but in a foolish way. I added this at the top of views.py:

SAFE_STATE_LIST = (
    list(State.objects.values_list('state_abbr', flat=True)) +
    list(State.objects.values_list('state_fips', flat=True))
    )

This setup allowed the whitelist to be built just once. But since it was evaluated at Django initialization time, that meant that the whitelist would be empty for testing in Travis, where the view would slap a 400 on any state query, behaving as if there were no states, even when a test loaded fixtures or built its own valid state objects.

This is why an initial_data fixture was the only test-loading strategy that worked in Travis, because it got auto-loaded before views.py was initialized.

So here's a toast to Django 1.9+ and the end of initial_data fixtures entirely!

travisty

(noun) A false assertion that the Travis CI service is a travesty.

[coveralls]

Coverage decreased (-0.5%) to 99.473% when pulling 8909055 on update-countylimit-tables into 897a887 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 28e7ea2 on update-countylimit-tables into 897a887 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling f871196 on update-countylimit-tables into 897a887 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 3e9ff8c on update-countylimit-tables into 897a887 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9051630 on update-countylimit-tables into 897a887 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling ffbbf2c on update-countylimit-tables into 897a887 on master.

[hillaryj]

A+ atonement game 🏅