removing unused commented code
added lineage tracking code
Removing potential additional shuffle dependency where an already partitioned RDD[(Vid, VD)] is repartitioned.
removing completely unnecessary map operation.
Added bitset to kryo register
Merge pull request #43 from amplab/FixBitSetCastException

Fix BitSet cast exception
Merge pull request #41 from jegonzal/LineageTracking

Optimizing Graph Lineage
Merging with upstream master.