Add logging example and some readme fix ups

[lukehinds]

Just getting my feet wet, so some typo fixes and a logging env example.

[leonjia0112]

Thanks for fixing the typo. 👍

To pass the format check, try

$ rustup component add rustfmt-preview
$ cargo fmt --all -- --check

It would fix it for you.

[frozencemetery]

Thanks @lukehinds, this looks good! Don't worry about the Travis failure; rustfmt seems to have changed under us. Will merge shortly.

[lukehinds]

Thanks @leonjia0112 , so the lint errors have crossed over from the master branch.

I can fix these by just running with --check, may as well do this in this branch and we can look at the diffs.

[frozencemetery]

Hah, that works too :)

[lukehinds]

Sorry @frozencemetery missed your previous comment somehow (comment race condition!). All looks good now.