Switch tests to Jest

I believe this will make contributions to this project easier. Recently I created a PR and wanted to add some tests but noticed that there are no tests for any interactions yet so I would need to make a choice of a mocking framework (Sinon?) but ideally I'd just jump into writing tests. Jest comes as a feature-reach testing framework that has everything needed to test React components bundled (snapshot testing is amazing BTW, mocking, promises etc.).

Would you consider switching to Jest if I would create a PR?