Add recommended config

[brettz9]

• Enhancement: Add "recommended" config which auto-adds plugins and all current rules (one as a warning); fixes Add recommended config #69
  - Linting: Rename eslintrc to include recommended extension
  - git/npm: Add package-lock.json to ignored files
  - npm: Add recommended package.json fields (contributors, dependencies)
  - npm: Add peerDependencies as called for by ESLint
  - Travis: Add Node 12/ESLint 6 and Node 10/ESLint 5 tests

Your Travis file tests ESLint 2 and your README insists on a minimum version of 4, so I wasn't sure which one to fix (and thus which to use in the peerDependencies field which ESLint calls for).

As far as Node version, FWIW, your devDeps import-from and eslint can both be updated to the latest versions if you move to a minimum version of Node 8.

[brettz9]

Are you going to have time to take a look?

[Turbo87]

you are doing a lot of different changes in this PR which makes it significantly harder to review. can you split them up into dedicated PRs where each PR only changes one specific thing? 🙏

[brettz9]

I've removed the ES6 changes which were the bulk of the PR. The number of changes in this PR are much smaller now; they are just a handful of small changes instead. Is that ok?

I can submit the refactoring PR separately which has more changes, though of the same type.

[Turbo87]

you still have a list of things that it does in the description. adjusting the CI config is a separate thing, doing stuff with package-lock.json is too, peerDependencies is one, etc.

[brettz9]

Ok, I've changed to just handle one item in this PR. I can submit the others separately. Please review this one if you would.

[Turbo87]

could you add some documentation on how to enable this config in ESLint?

[Turbo87]

👏