Stampit and ES6

Stampit is ES5. Often people ask why there is no ES6 bundle. There are few reasons.

The main advantage of the ES6 is the import/export syntax which enables easy treeshaking. But.
- There is nothing to treeshake in stampit or @stamp/it.
- stampit is already 1.3KB gzipped.
Maintaining ES6->ES5 is quite hard in such a specific project.

We will rethink this policy as soon as there is a need which cannot be solved with ES5.