Downgrade eslint-formatter-pretty to support Node.js 8

[bendrucker]

eslint-formatter-pretty@4 requires node 10, and breaks compatibility with 8:

sindresorhus/eslint-formatter-pretty@2b21776#diff-168726dbe96b3ce427e7fedce31bb0bc

Noticed this in a failing test when upgrading tsd to 0.12:

/home/travis/build/bendrucker/snakecase-keys/node_modules/eslint-formatter-pretty/index.js:127
			} catch {
			        ^

SyntaxError: Unexpected token {
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:617:28)
    at Object.Module._extensions..js (module.js:664:10)
    at Module.load (module.js:566:32)
    at tryModuleLoad (module.js:506:12)
    at Function.Module._load (module.js:498:3)
    at Module.require (module.js:597:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/travis/build/bendrucker/snakecase-keys/node_modules/tsd/dist/lib/formatter.js:3:19)

[SamVerschueren]

I'm wondering if I should rather drop support for Node.js 8 instead. It's EOL since 31st of December 2019.

[bendrucker]

Totally fine too! I’d still recommend downgrading and publishing a patch, and then optionally requiring Node 12 and bumping the version here for that.

[SamVerschueren]

Fair point! Let me quickly release a patch and drop support for Node 8 in the next release.

[SamVerschueren]

Released as 0.12.1. Thanks for reporting and sending a PR :).