Breaking: drop support for Node v6

[kaicataldo]

refs #53

Now that we've dropped support for Node <8, I think we should also drop support here. I'd like to merge this, merge #53, and then cut a major release.

Edit: @ilyavolodin made me aware that Webpack depends on eslint-scope directly, and it appears that they still support Node@6. Maybe this isn't something we want to do yet?

This was discussed by the TSC, who resolved to accept this.

[aladdin-add]

pkg. engines need to be updated. :)

[kaicataldo]

@aladdin-add Thanks for the reminder!

For the team: do we care about this matching eslint/eslint? It looks like we treat each project independently in this regard.

[aladdin-add]

the packages that eslint depended should have a same/wider range. so I think it's fine to be as is.

[kaicataldo]

TSC Summary

eslint-scope currently supports Node >=4.0.0. This PR drops support for Node 4 & 6 since we have dropped support in ESLint core. There were some concerns raised about doing this, because Webpack relies on eslint-scope directly. I'm not sure how to proceed with this, so figured it was good to have the TSC make a decision.

TSC Question

Do we want to accept this?

[mysticatea]

LGTM.

For reference, Webpack 5 has dropped Node 6, too. (webpack/webpack#7593)

[kaicataldo]

Ah, in that case, I think we should be okay. @ilyavolodin just want to make sure you feel okay with this.

[kaicataldo]

This was discussed during today's TSC meeting and the resolution was to accept this.