int cannot cast to double cause an exception

[SimonSoftware]

On geojson_parser.dart on line 308/311 must use
LatLng((coords[1] as num).toDouble(), (coords[0] as num).toDouble()));
because if on geojson there's an integer coordinate the coords[1] as double doesn't work and raise an exception on iOS (physical or Simulator).

[efoertsch]

Also hit it on line 279 (and there is similar coed on lin 282)