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`)
That's a good idea, I'll give it a shot since I've got extra time on this card.