* Implemented a version check of npm to give a soft tip during the install procedure
and fixed gitignore

* Moved NPM check to method, it is only executed when you use NPM and the version is < 3.

* Minor formatting tweaks

* Simplify the code

* Remove unnecessary change

* fix: add yarn gitignores to template

* fix: add yarn gitignores to root

* fix: add wildcard to npm-debug.log ignore

The Contributing instructions in the README give my-app as the sample
app name when running `npm run create-react-app my-app`. This just adds
those directories to the .gitignore so they don't accidentally get
committed.

Test Plan:

```
npm pack
node global-cli/index.js testing --scripts-version /Users/vjeux/random/react-getting-started/create-react-app-scripts-0.0.1.tgz
```

make sure it shows

```
Creating the app testing at /Users/vjeux/random/react-getting-started/testing
```