Add es-check to make sure I'm transpiling correctly

[sebnitu]

Problem

I've been reading a lot about bundlers and their default behavior with ES6 and module imports. It'd be awesome to incorporate some kind of check to make sure my bundles are being output correctly.

Possible Solution

After reading this article: Lessons Learned From a Year of Fighting With Webpack and Babel, I got the suggestion to use es-check for making sure I'm outputting the correct versions in my bundles.

Additional resources:

• How to handle npm modules which include es6

[sebnitu]

This is no longer needed after #394