Tests

[the-overengineer]

Adds support for testing the SDK, including React components, through mocha and chai.
Adds coverage reporting via nyc.

Adds some tests for the basic building blocks of the SDK, allowing them to be used as an example for writing tests in the future.

Adds two modes of running tests:

• npm run test for one-time test run + coverage reporting
• npm run test:watch for running tests in watch mode, to be used in development

Fixes #7

[the-overengineer]

Hm, the issue seems to be that much of the ancient stack is not supported on old Node versions. @robertjd @typerandom are these old versions really necessary anymore? The bare-bones build process works there, we know as much, but I cannot seem to find decent replacements for some of the dev tools here, which require Node >= 4. Any change we could migrate Travis to test 4, 6 and 7? We're just pushing a built library anyway.

Everything works fine on version 4+.

Also, I added just some basic text examples for every type of object in the app. I can either test everything, but that will take a while, or we can go with a policy of adding tests when you touch something (and appropriately moving the minimum coverage percentage up as we go).