Map each N elements of an Array at a time.
mapper is called as cb(eltI, ..., eltJ) where I is multiple of n and J is I+n-1
Throws InvalidArgument if number of items in arr is not divisible by n.
mapper is called as mapper(eltI, ..., eltJ) where I is multiple of n and J is I+n-1
Source: stdlib.ngs:1118