Integrate minification utils for publishing browser libs via npm

* Should support es6 modules
* We could use uglify-js.
* Avoid using babel if possible.
* https://unpkg.com/ can then be sued for distribution

## sample but not working
package.json scripts:
```
"minify": "uglifyjs src/*.js -o dist/core-analytics.min.js -c -m --source-map \"root='../',url='foo.min.js.map'\"",
"release": "npm run build && mkdir dist && npm run minify"
```