* 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`.

* use safer/more aesthetic syntax

* fix typo

The launch configuration code provided is not compatible with VSCode since version 1.19.
The proposed documentation change is based on the response by a VSCode team member.

References:
https://github.com/facebookincubator/create-react-app/issues/3602#issuecomment-352075571
https://github.com/Microsoft/vscode/issues/40293#issuecomment-352017028

* docs: adding section about debugging tests

* docs: removing node-inspector references

* docs: replacing terminal command with npm script

* Update README.md

"subway" by itself is not a proper noun

* Add link to VS Code troubleshooting guide

* Update README.md

Fixed a small grammatical issue that I noticed while browsing the README today

* Change template manifest start_url to dot to make it react-router friendly

* Revert "Change template manifest start_url to dot to make it react-router friendly"

This reverts commit 02f53e81.

* Add a note about PWA manifest and client-side routing

instead of using `&&` to run multiple commands in `package.json`, guide users to use `npm-run-all`

This resolves #3272.

It's confusing: https://mobile.twitter.com/brianleroux/status/923581596720013312

h/t @brianleroux

The existing link lands on a 'this page has moved' placeholder that
doesn't redirect to the correct location. This PR replaces it with the
currently working URL.

Closes #3291

Correct manual proxy documentation

* Class fields to stage 3

Per 2017.07.27 TC39
https://github.com/tc39/proposals/commit/0bbbb08c3cdcc986d59b21782b70633329546042

* Be explicit that only the public part of the unified field proposal is available.

* Debugging in WebStorm

* Fixed formatting for shortcuts

* Added note about default URL

The service was rebranded to xervo.io and was completely shut down in April 2017

Fixing a small typo.