update code to scala 2.10
update copyright notice
update TODO list
split the LongHashSet interface from the concrete implementation
Implement a MemoryEfficientLongHashSet that stores small values in an IntHashSet
use an additional IntHashSet to store values below 0xffffffff
don't expose the ensureSizeFor function
add some comments
Fix getFollower/getPredecessor to only return real followers/predecessors.