React async compatible TextArea

[pfarejowicz]

Part of #216
Following the guide here: https://reactjs.org/blog/2018/03/27/update-on-async-rendering.html#updating-state-based-on-props

[christianvuerings]

Deploy preview for gestalt ready!

Built with commit d694fb1

https://deploy-preview-222--gestalt.netlify.com

[ghost]

	Warnings
⚠️	Bundle size increase

Filename	Size Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip
gestalt.js	🔺 0.0%	🔺 0.0%	264.54 KB	264.6 KB	59.05 KB	59.06 KB
gestalt.es.js	🔺 0.0%	🔺 0.0%	261.99 KB	262.05 KB	58.69 KB	58.69 KB

Generated by 🚫 dangerJS

[pfarejowicz]

Note: had to update the yarn.lock file following these steps to get tests to pass
enzymejs/enzyme#1600

[codecov-io]

Codecov Report

Merging #222 into master will increase coverage by 0.42%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
+ Coverage   61.05%   61.48%   +0.42%     
==========================================
  Files          40       40              
  Lines         796      797       +1     
  Branches      186      186              
==========================================
+ Hits          486      490       +4     
+ Misses        219      217       -2     
+ Partials       91       90       -1

Impacted Files	Coverage Δ
packages/gestalt/src/TextArea/TextArea.js	35% <100%> (+3.42%)	⬆️
packages/gestalt/src/ErrorFlyout/ErrorFlyout.js	80% <0%> (+60%)	⬆️

---

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 90178c1...d694fb1. Read the comment docs.