Require Node.js 10 and upgrade dependencies

[realityking]

Waiting for dependents/node-filing-cabinet#94 before this ready to merge.

This is mostly straightforwardly bumping dependencies and requiring Node.js 10.13+

Two other changes

• babel is only used to load test which are written as ESM. I replaced all of that with the simple esm package. This cuts down the dev dependencies nicely.
• I aligned the required Node.js version with that of PostCSS 8 so that when there's a release with Use PostCSS 8 and require Node.js 10 node-detective-postcss#76 it can be upgraded without bumping the major version again

[realityking]

@mrjoelkemp This one is ready to review

[mrjoelkemp]

@realityking excellent work getting all of the packages upgraded carefully. Thanks for the contributions. I just released v8.

[realityking]

Thanks for keeping up with it :)