Webpack 2 and Middleman 4

As of version 4, Middleman now supports a variety of front-end/JS tooling via the External Pipeline, outlined here. Previously Middleman only built assets via Rails’ venerable Asset Pipeline aka Sprockets. There is a lot that could be said about Sprockets and why it may or may not be a good choice for Middleman going forward, but even the core Rails team is building in a way to integrate new JS tools like Webpack [edit as of 3/17], and its clear which way the wind is blowing.