Consider replacing webpack by rollup

[blikblum]

Rollup provides the following advantages:

• smaller transpiled code due to avoidance of require calls [1]
• saner and smaller code for exported functions, e.g., it will not transpile clone(router.state.param) into (0, _dash.clone)(router.state.params). [2]

I'm willing to try the conversion, but discussing here first to see if is worth try

Disclaimer: for my apps i use webpack, so no problems with it at all. But as today, for libraries rollup has some advantages

1. https://nolanlawson.com/2016/08/15/the-cost-of-small-modules/
2. http://stackoverflow.com/questions/32275135/why-does-babel-rewrite-imported-function-call-to-0-fn