Rust Book Example Fix: Arrays, Vectors, and Slices

[jatinn]

In the Arrays, Vectors, and Slices section the last example warns about the slice syntax.

let a = [0, 1, 2, 3, 4];
let middle = a.slice(1, 4);     // A slice of a: just the elements [1,2,3]

This fixes it however I am not sure as to why the & is needed?

let a = [0, 1, 2, 3, 4];
let middle = &a[1..4];     // A slice of a: just the elements [1,2,3]

I would submit a PR but I think some explanation is required and I am not the best person to be explaining this. (Just started looking into rust now that its in v1 alpha)

[steveklabnik]

You need the & because we removed the auto borrowing. I've submitted a PR to fix, thanks!