Test mlz_jurisdiction

[jcushman]

Just flagging that the "mlz_jurisdiction" isn't currently tested, and likely contains a lot of stuff that isn't right, but potentially could be tested against https://github.com/f-mb/mlz-jurisdictions/blob/master/jurisdictions.json .

[mlissner]

Over in #130, there's some good discussion about this, but ultimately Jack was way out ahead on what's needed: Tests. To that, I'd also add: Documentation, but this feels relatively easy, aside from the lift of verifying and updating what's already there.