Closes #4932, Closes #4876

* No lock files prevents the use of yarn upgrade & outdated

* Update deps

* Bump Jest across the board

* Add safe postcss parser

Uglify is no longer maintained and has bugs not present in Terser (its successor)

* Update jest version

* Update babel-jest version

* Use testURL: http://localhost in jest configs.

* Update to jest version 23.5

This version of jest includes a fix for https://github.com/jsdom/jsdom/issues/2304

* "testURL": "http://localhost" is default with jest v23.5

- [x] Utilize webpack 4 development and production modes
- [x] Upgrade webpack dev server
- [x] Webpack 4 compatible release of thread-loader
- [x] Webpack 4 compatible release of HtmlWebpackPlugin
- [x] Webpack 4 compatible release of SwPrecacheWebpackPlugin
- [x] Webpack 4 compatible release of WebpackManifestPlugin
- [x] Update README
- [x] Update WebpackDevServerUtils
- [x] Update InterpolateHtmlPlugin
- [x] Update ModuleScopePlugin
- [x] Update WatchMissingNodeModulesPlugin
- [x] Move UglifyJS options to webpack 4 optimize
- [x] Move InterpolateHtmlPlugin to make it tapable on HtmlWebpackPlugin
- [x] vendor splitting via splitChunks.splitChunks (https://twitter.com/wSokra/status/969633336732905474)
- [x] long term caching via splitChunks.runtimeChunk (https://twitter.com/wSokra/status/969679223278505985)
- [x] Make sure process.env.NODE_ENV is proxied correctly to `react-error-overlay`
- [x] Implicit webpack.NamedModulesPlugin in dev config as its default in webpack 4
- [x] Disable webpack performance hints as we have our own filesize reporter
- [x] Replace ExtractTextPlugin with MiniCssExtractPlugin
- [x] Switch to css whole file minification via OptimizeCSSAssetsPlugin rather than per module css minification to gain performance

* Updated jest version.

* Add explicit dep on plugin-proposal-object-rest-spread to babel-preset-react-app

* Bump babel-related deps to beta.42

* Pass useBuiltIns directly to react-preset

* Try to fix CI

* Bump Jest elsewhere

* Bump Babel elsewhere

* Fix CI on Windows by writing .cmd file back

* Bump dependencies

* Use a more sensible way to compile error overlay

* Keep old chalk for global CLI

* Bump eslint-plugin-jsx-a11y

* Update index.js

* Update index.js

* Update package.json

* Don't use links for non-linky things

* Update dependencies in react-scripts

* Add first pass of working dependencies for babel-preset-react-app and react-scripts

* Bump more dependency versions

* Adjust more versions and edit fix options

* Restore functionality of old preset

* Disable Uglify in iframe webpack

* Apply prettier

* Re-enable cache in dev and clean deps

* Lock packages and move babel/core to dep in preset

* Bump babel-jest

* Re-enable uglify

* Nest forceAllTransforms correctly in webpack config

* Install babel-core bridge for jest

* Add jest-cli and babel-core bridge to make tests in react-error-overlay pass

* Re-enable transform-dynamic-import

* Add dynamic import syntax support back

* Use new babel in kitchensink

* Transform modules in test

* Revert "Transform modules in test"

This reverts commit 539e46a1.

* Attempt fix for ejected tests

* try this

* Add regenerator back

* Bump babel deps to beta.34

* Remove bad files

* Use default when requiring babel transform plugin

* Bump deps

* Try the fix?

* Oopsie

* Remove some weird things

* Run Babel on react-error-overlay tests

* Try fixing kitchensink

* Use new API for codeFrame

* Add missing (?) babelrc

* Maybe this helps?

* Maybe fix mocha

* I shouldn't have deleted this 

* update jest to 21.0.2 to support watchPathIgnorePatterns configuration

* update jest to 21.1.0

* Try bumping Jest

* Bump babel-jest

* Try to debug weird CI failure

* Remove debug code

* Bump other Jest packages

* ffs

* temp

* Revert "temp"

This reverts commit 62aec9ac.

 - babel-preset-react-app@3.1.1
 - create-react-app@1.5.0
 - eslint-config-react-app@2.1.0
 - react-dev-utils@5.0.0
 - react-error-overlay@4.0.0
 - react-scripts@1.1.0

* Switch to Yarn Workspaces

* Feedback

* Move flowconfig

* Use publish script

* Keep git status check

* Fix Flow without perf penalty

* Remove Flow from package.json "test"

* Try running it from script directly (?)

* Try magic incantations

* lol flow COME ON

* Try to skip Flow on AppVeyor

* -df

* -df

* -df

* Try to fix CI

* Revert unrelated changes

* Update CONTRIBUTING.md

* Open editor to exact column from build error overlay

* Update launch editor validations

 - babel-preset-react-app@3.1.0
 - react-dev-utils@4.2.0
 - react-error-overlay@3.0.0
 - react-scripts@1.0.15

* Bump dependencies

* Downgrade source-map back to 0.5.x

Not sure what changed there but our bundle snapshot doesn't match with minor changes.
I couldn't figure out how to update it, and also whether we need to tweak getPrettyURL in response.

* Use production React version

* We cannot strip our own checks if production

* Keep the sourcemap during minify

* Prevent devtools pollution

* Add some comments

* sigh