Suggestion: Add a Cargo chapter

[jbiason]

I think it would be interesting to go through the basics of using an external library and generating a package of sorts.

[mquandalle]

👍

[deni64k]

👍

[arthurprs]

A first version could be a single small example and point the reader to http://doc.crates.io/guide.html

[steveklabnik]

This would be a great addition; I'd be happy to mentor anyone who wants to work on this!

[mark-i-m]

I could take a stab at this too 😄

@steveklabnik Does #949 look like the right direction?