Regression testing

[reecelucas]

What Does This PR Do?

• Adds visual regression tests for using jest-image-snapshot. Regression tests cover common built-in effects and transitions.

• Updates existing integration test suite.

• Migrates existing unit test suite to use Jest, and removes deprecated API methods.

• Updates all dependencies to latest stable, and updates Webpack config to use v4.

To run the regression test suite standalone, you can use: npm run test-regression. To run the complete test suite (unit, integration and regression) use npm run test.

[PTaylour]

Super cool. Ready for a review?

[PTaylour]

@reecelucas have ported the old chai tests to jest and mocked out webgl so that they don't need a browser.

I'm going to switch to yarn and add travis next week before merging.