Upgrade eslint, flow, jest (#2531)

Summary:
**Summary**

Trying to get rid of all these dependabot PRs. This upgrades aslant, flow and jest.

**Test Plan**

All output is still the same.

NOTE: The lint is broken due to rules that exist in fb but not externally. That should be fixed in another PR altogether.

Pull Request resolved: facebookarchive/draft-js#2531

Reviewed By: creedarky

Differential Revision: D22779270

Pulled By: mrkev

fbshipit-source-id: 732f926594a2214daa3558a28502b513b32dc1cf