Fixed Rob's issue #925.

Fixed Sum.scala wierdness and fixed style.
can you fix format? should be:

```scala
    if(tile.cellType.isFloatingPoint){
      n match {
        case Square(ext) => new CellwiseDoubleSumCalc(tile, n, bounds)
        case _ =>           new CursorDoubleSumCalc(tile, n, bounds)
      }
    } else {
      n match {
        case Square(ext) => new CellwiseSumCalc(tile, n, bounds)
        case _ =>           new CursorSumCalc(tile, n, bounds)
      }
      //etc
```