Add Jest

[StrikeForceZero]

Need to go through and remove chai references, then possibly swap out mocha and karma entirely

notes for myself when I come back to this:

https://github.com/react-boilerplate/react-boilerplate/blob/master/app/components/Img/tests/index.test.js#L36

<Img /> › should not adopt a srcset attribute

    TypeError: chai_1.expect(...).to.not.have.attr is not a function

      at Object.it (app\components\Img\tests\index.test.tsx:31:54)

related to #5

[wer32]

Wow it works. I've migrate that pull request to my project. Thank you for your work!

[SimpleCookie]

I got nothing to add, just wanted to say good job! Keep at it.
I'm just about to give this repo a try. I'd love to contribute, but not sure if I can.