[1556] Rollup + Buble for Nuxt.js

I wish when I was using Nuxt.js that I was using Rollup + Buble. The output code is MUCH cleaner, leaner, and faster.

Webpack + Babel leads to heavier code in order to be spec-compliant. To work with Babel, you have to work within a few limitations, but it's no problem. I recently migrated a project from Babel to Buble after fixing some parts of the code to work within Buble's limitations, and the result are AWESOME. I shaved my bundle size and the code is faster and cleaner.

Buble (with Rollup for bundling) is simply awesome, it makes me feel like Webpack + Babel is like strapping weight on a chain to my feet rather than shoes with wings.