UTM reprojection

Updates the Geotrellis GTFS parsing endpoint to detect the UTM zone for the incoming data and reproject that data to the correct UTM zone. Further details in the code comments.

I've manually verified Zhengzhou and Philly, and they both end up with the proper projection (for the curious, you can generate a UTM SRID via something like: `'32' + <'7' if southern hemisphere, '6' if northern> + zone_num`)
I've updated with a basic test; it's a bit of a cop-out since in order to fully test we need to create (and perhaps destroy?) a test database, which was more than I wanted to wrangle with on the remaining time for this card. But it does test the validity and existence of the UTM boundary data.