Update us-mn-carver.json

Carver County recently passed an Open Data initiative. They have an open data portal here: http://data.carver.opendata.arcgis.com/. The endpoint in the JSON file should replace the previous endpoint, which was hidden behind a proxy. This page has more info on the address standard they use: http://metrogis.org/MetroGIS/media/gis-documents/how-do-i-get/MetroGIS_Address_Standards2010.pdf