Use imports instead of requires in tests

[WesCossick]

This replaces the use of require() in test files. It also removes some now-outdated Babel plugins.

[codecov]

Codecov Report

Merging #340 (48de08f) into master (031cc6a) will increase coverage by 78.03%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #340       +/-   ##
===========================================
+ Coverage    0.00%   78.03%   +78.03%     
===========================================
  Files           7        7               
  Lines         396      396               
  Branches      111      111               
===========================================
+ Hits            0      309      +309     
+ Misses        396       87      -309     

Impacted Files	Coverage Δ
src/screens.ts	96.47% <0.00%> (+96.47%)	⬆️
src/utils.ts	97.22% <0.00%> (+97.22%)	⬆️
src/default-settings.ts	100.00% <0.00%> (+100.00%)	⬆️
src/process-arguments.ts	100.00% <0.00%> (+100.00%)	⬆️
src/print-pretty-error.ts	100.00% <0.00%> (+100.00%)	⬆️
src/error-without-stack.ts	100.00% <0.00%> (+100.00%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 031cc6a...9fbe153. Read the comment docs.