Mass dependency upgrade

[smashwilson]

A bunch of our dependencies have fallen behind by several major versions at this point. To prepare for enabling Greenkeeper, I'm upgrading everything but Relay all in one fell swoop.

I'm excluding Relay dependencies because I know that 1.5+ breaks things and I wasn't able to determine how to fix it quickly the last time that I looked. We can do that in its own PR later.

While I'm at it, I'm locking all of our dependencies to exact versions in our package.json file.

• Semver-compatible upgrades have caused us problems in the past. It's one of the ways that atom/github has ended up being broken on Atom stable.
• The version of npm that apm uses is too old to respect package-lock.json files, which are intended to deal with this problem.
• Greenkeeper will send us pull requests for any new dependency versions that are published anyway, so locking versions won't prevent us from knowing about dependency updates.

The eslint upgrades will cause some linter changes as well, so the diff is likely to be quite noisy.