Rewrite build process to use Webpack or Gulp

[addyosmani]

A few years ago we switched to a build setup using Yeoman and Grunt. Although I've just updated this to build correctly once again, the Grunt setup feels a little dated.

If someone would like to help with a migration to Webpack or Gulp, I'd be pretty up for landing it.

[jpumford]

I'd like to do this. This book was so helpful to me when I was learning JS. Thanks!

I noticed that the project is requiring node >=0.8. Are you comfortable with requiring latest LTS (8.9.0) of node? We could also use webpack's required node version (>=5.10)