chore(deps-dev): upgrade to ESLint 6 and friends

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

• Switched from airbnb to airbnb-base (because we don't use React)
• Probably the largest change was to fix the no-async-promise-executor lint.