Upgrade functionality tests to latest data-es6.js file.

[realistschuckle]

The content of assets/data-es6.js has grown stale. The new content at data-es6.js has a new and better format. This site needs to update to that new content and adjust the tests module in _src/modules/tests.js to work with the new format of data.

The new data-es6.js also has a dependency on an Object.assign polyfill that needs to come along with it.

Make sure to change the tracer support of the "let" keyword from true to false.