Initial commit of WIP PR for terasort benchmark.

As discussed on list, this is a WIP for Spark Terasort.
@ehiggs [copyToArray API](http://www.scala-lang.org/api/current/index.html#scala.Array@copyToArray%28xs:Array[A],start:Int%29:Unit)
`takeRight` may not be the proper choice, but `copyToArray` don't work as you thing, right?
Though `copyToArray` does not affect TeraSort's logic.
```
scala> a
res6: Array[Int] = Array(1, 2, 3, 4, 5)

scala> val foo = new Array[Int](2)
foo: Array[Int] = Array(0, 0)

scala> val bar = new Array[Int](3)
bar: Array[Int] = Array(0, 0, 0)

scala> a.copyToArray(foo, 0, 2)

scala> a.copyToArray(bar, 2, 3)

scala> foo
res9: Array[Int] = Array(1, 2)

scala> bar
res10: Array[Int] = Array(0, 0, 1)
```