Comprehensive Rust v2 by djmitche

I'm very happy to announce that Comprehensive Rust has received a major upgrade! Thanks to an enormous effort by @djmitche on GitHub, we now have a version 2 of the class published online: https://google.github.io/comprehensive-rust/!

The new version has:

• More exercises! 20 exercises spread over 4 days (compared to 11 exercises before). This was the feedback we heard most often: give us more exercises!

• Better structure to fix continuity errors. We fixed a few problems earlier, but this rewrite is much deeper. Please let us know if you find things that are ordered poorly!

• Four days of content instead of 3 days. Because we've expanded the content, Rust Fundamentals is now 4 days instead of 3. We also run 6 hours per day instead of 5. This is based on course feedback where people told us that they hit a wall on Day 3 — the new pace is more gradual.

The classes on Android, Bare-metal, Concurrency, and Chromium are not affected.

We hope you like the new material!