### Recursive Range Sum

Create a class `RangeSum`

with a public static method `sum`

that accepts a single `int`

value and returns the sum
of all the integers in the range 1..value as an `int`

.
So, for example, given the input 10 you should return 55: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10.
You can reject arguments less than or equal to 0 and ones greater than 128 by throwing an
`IllegalArgumentException`

.

You should submit a *recursive* solution.
The range sum of 1 is 1, and this represents the base case.
The range sum of n is n + the range sum of n - 1, and this represents the recursive step.