Add calss to mark OSM nodes Ids that are being used. Uses 1 bit per Id
to mnimize memory use. Abandoned the idea of using google sparsetable.
Merge pull request #19 from valhalla/gdg

Properly setting offset and counts
Merge pull request #20 from valhalla/dwn

NodeIdTable update
Added some more debug
Merge branch 'master' of https://github.com/valhalla/mjolnir into gdg