Update all of our dev dependencies in one fell swoop

[smashwilson]

This is me running through npm outdated and updating everything in devDependencies to @latest at once. Because these are all dev dependencies, a green build and proper coverage reporting are strong indicators that this is fine to do.

[codecov]

Codecov Report

Merging #1891 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1891      +/-   ##
==========================================
+ Coverage   91.07%   91.08%   +0.01%     
==========================================
  Files         185      185              
  Lines       10639    10719      +80     
  Branches     1575     1575              
==========================================
+ Hits         9689     9763      +74     
- Misses        950      956       +6

Impacted Files	Coverage Δ
lib/views/pr-commits-view.js	58.33% <0%> (-8.34%)	⬇️
lib/models/author.js	66.03% <0%> (-6.69%)	⬇️
lib/models/operation-state-observer.js	97.14% <0%> (-2.86%)	⬇️
lib/models/commit.js	91.91% <0%> (-2.77%)	⬇️
lib/composite-git-strategy.js	100% <0%> (ø)	⬆️
lib/models/remote.js	100% <0%> (ø)	⬆️
lib/atom/uri-pattern.js	100% <0%> (ø)	⬆️
lib/controllers/issue-timeline-controller.js	0% <0%> (ø)	⬆️
lib/models/patch/file.js	100% <0%> (ø)	⬆️
lib/controllers/pr-timeline-controller.js	33.33% <0%> (ø)	⬆️
... and 8 more

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