Remove rnpm and add react-native config file

[FelipePaiva1992]

When I build my app using this dependence the CLI return me this warning: The following packages use deprecated "rnpm" config that will stop working from next release: react-native-spinkit: https://npmjs.com/package/react-native-spinkit

Please notify their maintainers about it. You can find more details at https://react-native-community/cli/docs/configuration.md#migration-guide.

This PR it`s basically this update

[mylylyl]

https://github.com/react-native-community/cli/blob/master/docs/configuration.md

[maxs15]

Thanks @FelipePaiva1992, merging it 👍