Create cats.data.NonEmptyStream?

[ceedubs]

Once #1087 and #1088 have been completed, I think that we should probably drop OneAnd from cats. At that point, I think that NonEmptyStream would be the only data structure referencing it. We can probably drop NonEmptyStream at that point, but I created this issue to let people weigh on if NonEmptyStream is something that they would really want in cats. I suspect that it's not really used.

[wjlow]

I'm at the point where I would like to have NonEmptyStream currently.

I have a Stream[A] at the moment that I know is never empty and A is a Semigroup without a Monoid. Would be good to be able to reduce it safely without having to do stream.reduce(_ combine _), which is unsafe.

Edit: In retrospect, since I know I'm going to iterate through the entire Stream using reduce, I could just convert it to a NonEmptyVector instead.

[johnynek]

@wjlow or you can use OneAnd right? https://github.com/typelevel/cats/blob/master/core/src/main/scala/cats/data/OneAnd.scala

[wjlow]

Yes, thanks!