Add documentation for customizing Bootstrap theme

* Document debugging in the browser.

* Styling

* Add note about when to import bootstrap CSS.

* Tweak

* Update flow configuration documentation

The documentation was missing creating the .flowconfig file

* Update flow configuration documentation

Adding in suggested changes

* Wording

* Wording

* add a comment about NODE_ENV value set to 'production' during build step

https://github.com/facebookincubator/create-react-app/issues/790#issuecomment-281986264

* Move words around

* Add note for using CHOKIDAR_USEPOLLING in virtual machines to enable HMR

* Use br in react-scripts template README md

* Use br in md for new line breaks

* Update troubleshooting HMR to allow for VMs running Windows

* Fix up the instructions

Update links to jest expect function.

* update CSS preprocessor instructions
- Windows shell users should note that running two programs simultaneously is not supported.

* fix the order of SASS build step
- the suggested build step with integrated CSS preprocessing is wrong. The SASS preprocessor should run first, then the react-scripts build will pick the up-to-date final CSS

* Add tweaks from PR discussion

* Tweak syntax doc

* Shorter version

* added how to disable autoprefix feature in doc

* Just link to the doc

* reactjs/redux#2004 List features beyond ES6 supported by create-react-app

* Add more info

* Add SASS support documentation #1007

* Change SASS section title to more generic label

* Fix link in Table of Contents

* Chain build-css with watch-css script, fix typos

* Update Sass and Less naming style

* Fix wording, remove offensive words

* Slightly rewite

* Suggest jest-enzyme for simplifying test matchers

* Update README.md

* Update README.md

* Add Advanced Configuration section

* Reference package.json instead

* Add HOST, HTTPS, and CI

* Switch wording from Amazon to a CDN

* Add test runner comment

* Add top-level README link

* Simplify wording

* Link to relevant docs

* Link to apps

* Add .env link

* Simpler links

* Add a CI flag note

* Fix paths in CSS files when homepage is set to "./"

In the production build, ExtractTextPlugin is used to generate a separate CSS file instead of injecting style through JavaScript. This plugin does not work well by default with nested output structure. To fix it, we give it a relative publicPath pointing to the build folder.

* Add section in README to explain how to make builds deployable anywhere

* Apply review requested change

* Apply review changes 2

* clarifying the use of custom environment variables

* Tweak

Updated README.md to refer to the current rebranding.

* Add ESLint config for VS Code users

* Update VSC ESLint note to a better solution 

Update VSC ESLint note to a better solution as discussed in Pull Request

* Reflect websocket proxy support on README

* Add 'the'

Per final comment in #372

`Snapshot rendering should actually be pretty stable / useable after React 15.4.1.
See this post for more info.`

* Added Rails link to User Guide

* docs: unify sections for rails and node backend integration

* docs: fix faulty link and indentation

* Add causes of dev server not detecting changes

Add causes of `npm start` not detecting changes to Troubleshooting chapter of User Guide

* Reworded slightly

* Update README.md

* Adds note on how to resolve file or directory not found errors for heroku deployments

* Style tweaks

* Add "Changing the Page Title" to User Guide

* Add link to main README

* Add syntax highlighting configuration guide.

* Update link.