Enable _.range() to accept a 0 for step

Enable `_.range()` to accept a `0` for `step`, for initializing arrays such as `[0, 0, 0, 0, 0]`, `[-1, -1, -1, -1, -1]`, useful in many use cases where you need an array which defaults to a basic value.

I don't know how to write tests (bad... I know), but I have tested all of the function's behaviors and everything is still intact, including "negative direction" arrays.

Cheers.