Upgraded from Babel 6 to Babel 7.
The only significant change seems to be the way `@babel/plugin-transform-classes` handles classes differently from `babel-plugin-transform-es2015-classes`. In regular mode, the former injects a `_createClass` function that increases the bundle size, and in the latter it removes the safeguard checks. However, this is okay because we don't all classes in new features, and we want to deprecate class usage in the future in the react repo.
Co-authored-by: Luna Ruan <luna@fb.com>
Co-authored-by: Abdul Rauf <abdulraufmujahid@gmail.com>
Co-authored-by: Maksim Markelov <maks-markel@mail.ru>
The React Native build does not minify error messages in production,
but it still needs to run the error messages transform to compile
`invariant` calls to `ReactError`. To do this, I added a `noMinify`
option to the Babel plugin. I also renamed it from
`minify-error-messages` to the more generic `transform-error-messages`.
