Polygon type does not support multiple holes

[mick-h]

Polygons in Rethinkdb support having multiple holes, but the driver will error when parsing them with a CaseClauseError. This appears to be due to to the RethinkDB.Pseudotype.Geometry.Polygon struct assuming there will only be one hole or no hole. The struct probably can stay the way it is but inner needs to be a list of lists of coordinates, rather than just a list of coordinates. The parser would need to be updated, and I'm not sure what else will break.