Fix bug where serializer wasn't being called
Re-add IndexedRDDBenchmark with some modifications
Benchmark serialized ImmutableVector
Reuse A object in benchmark
Benchmark Array[(Int, Int)]
Use ByteBuffer instead of BAOS for deserialization

This speeds up serialized ImmutableVector scans by 2x, but we're still
10x slower than scanning an array of boxed objects.
Access field of objects in scan benchmark