Adding Zillow shapefiles for MA (as retrieved from http://www.zillow.com/howto/api/neighborhood-boundaries.htm), though ZillowNeighborhoods-MA.shp.xml was subsequently run through dos2unix, and ZillowNeighborhoods-MA.geojson was produced from ZillowNeighborhoods-MA.shp, using the ogr2ogr utility and the following webpage: http://ben.balter.com/2013/06/26/how-to-convert-shapefiles-to-geojson-for-use-on-github/