Guide Redux: Pointers

This is super, super WIP, but I'm going to go get lunch for a while, and figured I'd toss my work up here in case anyone wants to see my work as I do it.

This contains a new introductory section explaining the basics of pointers, and some pitfalls that Rust attempts to solve. I'd be interested in hearing how my explanation is, as well as if this belongs here. Pointers are such a crucial concept, I don't mind having a beginners' section on them in the main docs, even though our main audience is supposed to understand them already. Reasonable people may disagree, however.
I think the word "dereference" is fine. It means the same thing in Rust that it does in every other language with pointers/references. And I like the bolding of the word, it highlights the fact that this is a potentially unfamiliar but important term that's being introduced for the first time.

I do agree though that this might use some elaboration in case the reader is not in fact familiar with pointers/references already.

> We can **dereference** the pointer by using the `*` operator. Dereferencing a pointer means accessing the value at the location stored in the pointer. This will work: