Switch to add-module-exports

In 1.0 this preset used plugin-transform-es2015-modules-commonjs for making export default more usable with require but modules with default and non default exports were actually producing odd results. Starting from 2.0 we use plugin-add-module-exports instead which does provides similar exports default behavior with require but only when there is just default export (type exports are fine) that way other exports are still available when imported through require.