Book: Small grammatical and stylistic edits to book
I've been reading [the book](https://doc.rust-lang.org/book/) and noticed a few small grammatical and stylistic issues which I've rolled into this pull request.
I'm not sure if I should do so many small, unrelated edits in a single pull request but it seems like a lot of overhead for each small edit. Maybe one commit per edit but one pull request per file/section? Feedback is very much appreciated as this is my first pull request ever!
r? @steveklabnik rollup
projects / rust.git / commitdiff