Better? wording for unwrap
Better? wording for unwrap

As a novice it took some time to get it. Splitting the comment makes it easier to me. What do you think?
chriskrycho/rust-by-example,realcr/rust-by-example,chriskrycho/rust-by-example,jinyuanxie/rust-by-example-cn,rust-lang-cn/rust-by-example-cn,aakloxu/rust-by-example-cn,mdinger/rust-by-example,mdinger/rust-by-example,jinyuanxie/rust-by-example-cn,realcr/rust-by-example,rust-lang-cn/rust-by-example-cn,aakloxu/rust-by-example-cn