* 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
* 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
