Good Idea: Throw into debugger on fail?

[mdornseif]

Besides some boilerplate, I added

if (!condition) {
    debugger // <--- this
    throw Error(message);
  }

I'm not really sure if it is a good idea to have something like this in production code, so I created a separate NPM package.
But I want you to be aware of this and if you decide to roll it into assertate that's also fine.

Please don't hesitate to close / reject this PR.