Port Foundation's javascript modules to use ES2016 dependency management

[kball]

We want to bring Foundation's JavaScript dependency management up to 2016.

Some challenges will include:

• Some of the utilities are not well encapsulated
• We still need to generate code that will work for folks without a build system, just inline including the various components.

However, I think the benefits will far outweigh the costs. Among other items, this should fix https://github.com/zurb/foundation-sites/issues/7386 and make it way easier to integrate Foundation components into other systems. It will also lay the groundwork for easier refactoring of Foundation down the road (jQuery removal, I'm looking at you!)

[kball]

That's a really good point @DaSchTour, I'll make the update. Any other feedback/improvements you recommend?

[kball]

@DaSchTour update made... definitely would additional feedback.

[DaSchTour]

@kball for the first step I think this is enough. I personally always use export class, export function and so on. But that's a mater of taste. As I've seen the abstract plugin class I would love to make the move from this state to TypeScript. I think it's worth to take a look into the usage of this and _this and where arrow functions should be used. But I think this should be done in a further step of refactoring. With transition to TypeScript I would also suggest adding TSLint with their recommended settings. Running the fixer once will directly add a lot of good practice, but I think that will be only small style improvements. But as I said I would see this in a later step, to avoid breaking everything ;)

[kball]

An initial PR has landed at #9965! @DaSchTour and @gakimball would love your reviews & feedback, as well as anyone else who would like to take a look.

[kball]

9965 has been merged! This issue can be closed. Super excited about the possibilities this opens up.