Updated to use fixed version of mapnik for OSX
Updated to use fixed version of mapnik for OSX

tomhughes/mapnik-vector-tile,mapbox/mapnik-vector-tile,tomhughes/mapnik-vector-tile,mapbox/mapnik-vector-tile,tomhughes/mapnik-vector-tile,tomhughes/mapnik-vector-tile,mapbox/mapnik-vector-tile,mapbox/mapnik-vector-tile