Merge pull request #34 from mapzen/dwn

Add tiling to pbfgraphbuilder.
Fixed id assignment
Merge pull request #35 from mapzen/gdg

Fixed id assignment
Update so we can get length along a vector of PointLL without having
to copy to Polyline2
Change edge_id to edge_index since the first outgoing edge is
in the same tile and level as the node there is no need for full
graph Id.
Merge remote-tracking branch 'origin/master' into dwn