chore(webpack): fit to webpack v2 best practices
chore(webpack): fit to webpack v2 best practices

According to [Webpack 2 best practices](https://webpack.js.org/guides/migrating/) rather than using the `?options` the more explicit `options` prop should be used.

(Really just a minor thing :wink:)
ocombe/ng2-translate,ngx-translate/core,ngx-translate/core,ocombe/ng2-translate