Rust: the "Minigrep" Example Program

I won’t provide a writeup for this, because it’s a lot of code, and the Rust docs already comments on it extensively.

However here’s my finished minigrep program: https://github.com/caveofprogramming/rust/

And here are the corresponding pages from the Rust docs: https://doc.rust-lang.org/book/ch12-00-an-io-project.html