Added a number of very fast, memory-efficient data structures: BitSet, OpenHashSet, OpenHashMap, PrimitiveKeyOpenHashMap.
Merge branch 'hash1' of https://github.com/rxin/incubator-spark into rxinBitSet
Adding logical AND/OR, setUntil, and iterators to the BitSet.
Switching to the @rxin BitSet implementation for VertexSet Value tables.
Merging with upstream master.
Merge pull request #44 from jegonzal/rxinBitSet

Switching to VertexSetRDD to use @rxin BitSet and OpenHash