Start writing tests for the components

[shawninder]

1. We want to avoid breaking things by accident as we make more and more changes with more and more devs
2. We want to enforce a common set of standards across all of our components
3. We want to make our capabilities and limits more explicit and tractable
4. We want to be equipped to produce troubleshooting tests or even TDD, should the need arise, rather than to have to start from scratch during an emergency

This issue is about the first step, which is to get some basic sanity tests in:

• Do all components render without errors or warnings
  • using default and minimal props?
  • using full-fledged nested extreme props?
• Is the code properly linted?
• Are the bundled asset sizes within reason?

And we can crown this achievement with a humbling code coverage badge on the readme…