Revert using Babel.

[ksaaskil]

• Change @types/node to @types/node@8 so we aren't accidentally assuming Node 12 when compiling TypeScript
• Delete Babel
• Revert back to compiling both types and JS with tsc
• Using Babel with the runtime plugin for polyfills is great but currently it does not support specifying the Node.js version so everything gets polyfilled (Use babel runtime plugin to polyfill instead of requiring core-js. #164), therefore skip using Babel for now and maybe set @types/node@6 in a future PR

[codecov-io]

Codecov Report

Merging #165 into dev will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##              dev     #165   +/-   ##
=======================================
  Coverage   89.27%   89.27%           
=======================================
  Files          42       42           
  Lines        1426     1426           
  Branches      328      328           
=======================================
  Hits         1273     1273           
  Misses        153      153

Impacted Files	Coverage Δ
packages/unmock-node/src/serialize/index.ts	90% <100%> (ø)	⬆️

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