Update learn/get-started article so it uses ferris-says version 0.3.1 #1736
Description
What needs to be fixed?
Introductory article uses an old version of dependency ferris-says with very big unsoundness bug. It should be updated to a new version where it is fixed, otherwise someone who is new to rust could look at the source code of this dependency and get very wrong ideas about unsafe and &str.
Page(s) Affected
https://www.rust-lang.org/learn/get-started
Suggested Improvement
Update this article so it uses new version of dependency and change sample code as API changed slightly. I am willing to provide a PR for that.