Export only ES modules

[pago]

By now ES modules are a well supported standard and can be used by the browser as well as Webpack, Rollup and other bundlers. Melody itself doesn't benefit from being exported as CJS.

We can simplify our tooling and avoid mistakes for our users by switching to ES modules and ignoring the CJS use case.

This is a breaking change.

[ayusharma]

I think we can also drop Node 6 support as it is going to END OF LIFE in April 2019.