* Update `babel-plugin-transform-object-rest-spread` to v6.19.0
The `babel-plugin-transform-object-rest-spread` v6.19.0 update will
allow us to remove the `babel-plugin-transform-es2015-destructuring` and
`babel-plugin-transform-es2015-parameters` as the object rest spread
transform will now work standalone and not require additional tranforms
* Remove unnecessary babel transform plugins from babel-preset-react-app
The `babel-plugin-transform-object-rest-spread` v6.19.0 update makes
these plugins unnecessary, as v6.19.0 can be used stand-alone
* Update dependencies
* Use published version of eslint-config-react-app for development
We dogfood on our eslint-config-react-app by using it as our ESLint config,
but installing it from the local folder causes problems when its peerDependencies
are updated, because npm won't update it unless the version number changes.
Use the published version for dogfooding so it can be installed from npm.
* Disable ES2015 transforms based on node version using babel-preset-env
* pass major version number for node to babel-preset-env instead of version string
* use parseFloat() instead of parseInt() to parse node version
* fixed style nits
