CRS annotation
--------------

   >>> import geojson
   >>> import geojson.crs

   By default, no CRS information is present. One should assume WGS84.
   >>> geojson.Point([0.0, 0.0])
   {"coordinates": [0.0, 0.0], "type": "Point"}

   Including crs
   >>> crs = geojson.crs.Named(properties=dict(name="urn:ogc:def:crs:EPSG::3785"))
   >>> point = geojson.Point([0.0, 0.0], crs=crs)
   >>> point
   {"coordinates": [0.0, 0.0], "crs": {"properties": {"name": "urn:ogc:def:crs:EPSG::3785"}, "type": "name"}, "type": "Point"}

   >>> geojson.dumps(point, sort_keys=True)
   '{"coordinates": [0.0, 0.0], "crs": {"properties": {"name": "urn:ogc:def:crs:EPSG::3785"}, "type": "name"}, "type": "Point"}'


