A build step to apply ES6 transforms?

[gaearon]

I intend to keep using some ES6 features in this code.

If you're using JSX, you can specify harmony: true (jsx?harmony in Webpack) in your JSX build step to get them for free. If not, I don't mind accepting a PR that adds a build step before publishing to NPM; however I won't accept a PR downgrading to ES5.

[gaearon]

This is now done with UMD build in dist.