Remove direct react dependency, cleanup unused dependencies, upgrade webpack-cli + sass

[acusti]

the direct react and react-dom dependencies cause react and react-dom 16 to be installed when adding react-code-input to a react v17.x application, so i removed the direct react and react-dom dependencies, keeping them only as peer dependencies (fixes #75). storybook still takes care of installing them so that npm start works, and yarn build still works. in addition:

• removed unused dev dependencies: extract-text-webpack-plugin, node-sass (already have sass as a dev dependency), react-addons-test-utils, react-bluekit, webpack-dev-server (fixes #93)
• added prop-types to peer dependencies (there is a direct import from prop-types in ReactCodeInput.js)
• upgraded to latest v3 version of webpack-cli (prepares for the possibility of upgrading storybook, which otherwise leads to https://github.com/webpack/webpack/issues/8082)
• upgraded to latest version of sass
• upgraded circle CI’s docker image to the latest node docker image

[codecov[bot]]

Codecov Report

Merging #152 (fe4ae2d) into master (2599c5d) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #152   +/-   ##
=======================================
  Coverage   96.55%   96.55%           
=======================================
  Files           2        2           
  Lines         145      145           
  Branches       41       41           
=======================================
  Hits          140      140           
  Misses          5        5           

Impacted Files	Coverage Δ
src/ReactCodeInput.js
src/utils.js
ReactCodeInput.js	96.45% <0.00%> (ø)
utils.js	100.00% <0.00%> (ø)

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[austinbiggs]

Bump! Is there any chance that this will be merged?