Use variable encoding for ints, longs, and doubles in the specialized serializers.

Addressing issue in Graph creation

During graph creation, create eTable earlier

Addressing issue in Graph creation where a graph created with a vertex set that does not span all of the vertices in the edges will crash on triplet construction.

Addressing bug in BitSet.setUntil(ind)

Addressing bug in BitSet.setUntil(ind) where if invoked with a multiple of 64 could lead to an index out of bounds error.

Changing image references to master branch.

Cleanup of VertexSetRDD

Shuffle replicated vertex attributes efficiently in columnar format

Specialize mapReduceTriplets for accessing subsets of vertex attributes

ByteCodeUtils.invokedMethod(), which we use in mapReduceTriplets, throws
a ClassNotFoundException when called with a closure defined in the
console. This commit catches the exception and conservatively assumes
the closure references all edge attributes.