Auto merge of #3733 - llogiq:clippy, r=alexcrichton

some clippy-suggested improvements

This fixes a number of [clippy](https://github.com/Manishearth/rust-clippy) warnings. It's mostly about readability, though a few changes could affect performance (though probably not measurably).

I've left out things to fix later; I thought I'd just push the first batch to see if you like it.

diff --cc tests/package.rs
Simple merge

diff --cc tests/publish.rs
Simple merge