Incorrect documentation of the `split` method

[rotmh]

The documentation of the split method suggest a return value of (first, last, [middle]), while it's actually (first, [middle], last).

nonempty/src/lib.rs

Lines 532 to 533 in 95d5cb1

	/// Deconstruct a `NonEmpty` into its first, last, and
	/// middle elements, in that order.

It can be fixed by either simply removing the "in that order" part, or by changing the listing to "first, middle and last elements".

I'd be happy creating a PR for fixing that, if you'd like.