Use osmtogeojson instead of osm-and-geojson for OSM data import

here are the pros:
* stable (no crashes on incomplete OSM data)
* provides real OSM [way-polygon detection](https://wiki.openstreetmap.org/wiki/Overpass_turbo/Polygon_Features)
* properly supports OSM multipolygons (simple as well as complex multipolygons)
* well [tested](http://github.com/tyrasd/osmtogeojson/blob/master/test/)
* proven on [overpass-turbo.eu](http://github.com/tyrasd/overpass-ide)
* faster(?)

cons:
* requires lodash
* doesn't provide geojson-to-osm conversion