Refactor to ES2015+

[zcei]

Just executed Lebab on the lib/ folder just for fun, and apart from mocking Tuna in lib/Effect.js:11 it seems to do its job quite well.

Applied:

• arrow (afterwards change the Tuna thing back)
• class
• let
• template
• default-param
• destruct-param

I have no clue how good your actual coverage is, but tests are still passing. Just wanted to mention it, as it might eases the burden for you to start off with the refactor.

Loving your sound projects ❤️

[adamrenklint]

Oh, that's cool. Could you submit a PR?