Add 2018-specific changes.

[ehuss]

Closes #91.

[ehuss]

Some notes:

• I have no idea where to place the page. I just stuck it at the end. Another option would be to place it directly in rust-2018/index.md but that didn't quite feel right.
• This is intentionally terse since it is intended to just be an overview. I'd be happy to add more detail, examples, links, etc. if you want.
• I'd be fine with dropping the Cargo section. The changes are relatively minor, and Cargo gives plenty of warnings in both editions.
• Feel free to suggest anything. This is the information I want to see, but I understand that the style/voice differs from the rest of the guide.
• I'll try to keep this list updated in the future. Some of these are actively being moved to 2015, and things like async/await will likely need to be added.

[ehuss]

Good points, thanks for taking a look!

[dwijnand]

This would be lovely to land, it took me quite some digging before I realised that NLL is edition 2018 only.

As a side note, I couldn't figure out how to specify the edition to rustc because it's not in rustc --help or in the guide anywhere, so I ended up looking it up in the cargo sources. (I later found it in rustc --help -v.)

[steveklabnik]

Thank you! People have been asking about this for a while. I think this is a fine place to put it, we can iterate if it turns out to be not ideal in practice.

[dwijnand]

Now that Rust nightly is fixed, could someone rerun the merge build for this so it deploys, please? Thank you!

https://travis-ci.com/rust-lang-nursery/edition-guide/builds/96925518

[ehuss]

I poked it, but it looks like it will be queued for a long time due to other jobs running. Oops, nevermind.

[dwijnand]

https://rust-lang-nursery.github.io/edition-guide/rust-2018/edition-changes.html 🎉