New ownership guide

This is the start of the new "Ownership" guide, to replace the lifetimes guide.

I'm still working on it, but I wanted to share my progress, as this guide is _very_ important, and I'd like as many eyes on it as possible. :smile: 
Yeah this is more a Rustdoc thing

Sent from my iPhone

> On Sep 9, 2014, at 22:13, mdinger <notifications@github.com> wrote:
> 
> In src/doc/guide-ownership.md:
> 
> > +a resource. If you need additional pointers, Rust offers a second concept:
> > +borrowing. Another reference may borrow the contents of a pointer which has
> > +ownership. Here's an example:
> > +
> > +```{rust}
> > +fn add_one(i: &int) -> int {
> > +    *i + 1
> > +}
> > +
> > +fn main() {
> > +    let x = 5;
> > +    println!("{}", add_one(&x));
> > +}
> > +```
> > +
> > +The `&x` on the seventh line creates a reference to `x`, and the `add_one`
> A little nitpicky but this would be nice with line numbers since you call one out. Playpen has them but rustbyexample doesn't embed them...not really in the scope of guide writing though...
> 
> \
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