Minor Description
It's a little inconsistent that the first two sqlContext.range() methods don't take a numPartitions arg, while the third one does.
And more importantly, it's a little inconvenient that the numPartitions arg is mandatory for the third range() method - it means that if you want to specify a step, you suddenly have to think about partitioning - an orthogonal concern.
My suggestion would be to make numPartitions optional, like it is on the sparkContext.range(..).
