* react-dev-utils/openBrowser now supports urls with 2+ params

Fixed #2047

* react-dev-utils/openBrowser: encode url before open the browser

* Support node scripts in BROWSER

Modify OpenBrowser.js to run node scripts specified with the BROWSER environment
variable . If the value of the BROWSER environment variable ends with '.js' a
child process is spawned to execute the script with node.js. Any
arguments passed to npm start are also passed to this script, as well as
the url where the app is served.
The command executed in the child process is:

node <pathToScript> [OPTIONS] <url>

Update User Guide.

* Tweak code style

* Pin dep

* Comment out 0.10 docs

* mv create-react-app/index.js -> create-react-app/creteReactApp.js

* update to modern code style

* var -> cosnt

* set trailing-coma to es5 for prettier

* Lint internal scripts with eslint:recommended

* Warnings r bad

* Fix openBrowser() when BROWSER=open on macOS

* Tweaks

Use a 'BROWSER' environment variable with npm start to specify which
browser to open. if the value of 'BROWSER' is not valid executable file,
don't open any browser.

Running `create-react-app` in a Docker container causes an unhandled rejection error in nodejs > 6.5 because the `opn` module tries to open a web browser in a system that doesn't have one. I figured this error could be safely ignored.

A previous commit renamed the apple script to open chrome from
`chrome.applescript` to `openChrome.applescript`. That created
a minor bug. Even when chrome was open with the client app,
`npm start` would open the client app in a new Safari tab on
macOS instead of re-using the open tab in chrome.

* Extract some utilities into a separate package

* Add utils dir to `files` in package.json

* Do not create an empty `utils` dir on eject