cleanup and change build system

[sgratzl]

Hi,

I cleaned up this repo a bit. Changes

• dedicated build system using rollup.js
• leads to an UMD compatible module export
• switch to ES6 module syntax
• fix test cornercase
• removed test library and use CDN instead

The resulting science object should be the same but friendlier to include by other libraries and websites

[curran]

@sgratzl Do you happen to know, is there any active fork of science.js that has a proper UMD build set up like this?

[curran]

Oh hey, nevermind, there it is! @sgratzl/science