Fix imports for Webpack

[atav32]

Like this: janpaepke#684

So that people don't have to keep doing this janpaepke#324 (comment) and this janpaepke#685 (comment)

[atav32]

A couple things to remember for the future

1. everything's easier when the module name and all imports reference a lowercase name
   a) changed "ScrollMagic" to "scrollmagic" (except the class name)
2. ES6 imports work better when ScrollMagic references the UMD versions of GSAP TweenMax
3. still need a Webpack/Babel alias to help animation.gspa.js find the module scrollmagic and point it to scrollmagic.js