Improved traversers

Added abstract class QueueBasedTraverser holds general logic for most
traversers.
Fixed errors in InfoKeepers.
Added InfoKeeper that uses IntToBoolean fastutil map to store Boolean
values.
Changed BreadthFirstTraverser so that first node is the node we start
traverse from (to be consistent with other traversals).
why is this an exception? the idea of recordInfo(id) is to record some info for a given node id. Here we are recording the neighbor info of id. i think this should call recordPreviousNeighbor()