Create an initial "map" component

Since the first part of this project is focused on creating a map of Montana nonprofits, we will need a full-window map component. Not sure what it should be built on, but Leaflet.js seems promising. Bonus points for relying on OSM for the mapping data since it's also a community-driven project. Additionally, we may be able to even augment OSM itself later with some of our data to make things simpler.