Added section on cargo new to "Hello Cargo!" chapter.

[jxcl]

r? @steveklabnik

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @steveklabnik (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see CONTRIBUTING.md for more information.

[steveklabnik]

{}s can be removed, this file still uses the old style, but i'd prefer to keep it the new style

[steveklabnik]

r=me after some nits

[steveklabnik]

@bos: r+ f49fd40 rollup

[steveklabnik]

@bors: r+ f49fd40 rollup

[steveklabnik]

Let's see if it works this time...

[steveklabnik]

It has!