Run cargo update

I have several local branches updating dependencies and addressing any
breaking changes (towards closing out rust-lang#1265).  I'd like to avoid
lockfile merge conflicts between those branches so I'm bumping all
semver compatible versions in this PR.

I'd like to let this bake in production for at least a few days before
opening PRs bumping major versions in `Cargo.toml`.

If this approach is too aggressive, or needs to be reverted, I can open
the other PRs more serially and look into breaking this upgrade into
smaller pieces.

Author: jtgeibel