Add preflight check to guard against wrong versions of webpack/eslint/jest higher up the tree (#3771)

* Run real scripts in local development

* Add preflight check warning

* I know what I am doing

* Move preflight check into individual scripts

This ensures we don't try to filter NODE_PATH twice, accidentally removing the now-absolute path.

* Slightly tweak the wording

* Fix lint

* Provide better defaults

* Let babel determine features to compile

* meh

* Remove setting of BABEL_ENV

* Revert "Remove setting of BABEL_ENV"

This reverts commit ee2db707.

* Set browsers to ie9

* Updating ESlint to ^4.15.0 and adding new rules to config

* remoning style rule and auto fixing breakages from new rules

* Removing implicit-arrow-linebreak style rule

* adding new rule to eslint config project

* updating react scripts eslint version

* Pinning version.

* Changing getter-return to warn

* Update package.json

* Update .eslintrc

* 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.

* Disables navigateFallback and updates the README

* Typos

* Updated a URL in a comment.

 - 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

* Add warning when HOST environment variable is set (#3719)

* Improve HOST environment variable warning message

* Adjust text and message

Closes #3719

* Always include destructuring transform

* Fix lint

* fix #2223 - [feature] Implement dotenv-expand to accept variable expansion in dot env files

* add to README TOC

* fix readme

* Update README.md

* Better documentation for setupTests.js when ejecting

When running `npm run eject` before creating `src/setupTests.js`, the resulting `package.json` file, won't contain any entry for it - and this is correct in my opinion, since otherwise Jest will crash - but it's useful to have it documented and avoid pointless waste of time.

* Added additional note about src/setupTests.js

Added another note about src/setupTests.js and `npm run eject` in Testing Components section

* Update README.md

* Update README.md

'more' and 'simpler' together is incorrect.

* add support to set REACT_EDITOR to none

* change README message

* change condition to avoid problems with editor being null

* move condition to avoid extra code

* Update README.md with a note that reminds users to prepend REACT_APP_ to their environment variables. 
* Based on #865, where Dan Abramov suggests the person who filed the issue create a PR with these changes.
* Took the language from [Adding Custom Environment Variables](https://github.com/facebookincubator/create-react-app/tree/master/packages/react-scripts/template#adding-custom-environment-variables)

Replace `provide a lot value` with `provide a lot of value`.