Fix jquery-bbq for browserify

@lzhang @elfreyshira @schutterp @civitaslearning/front-end 

Let's fix jquery-bbq to work with browserify:

- use `window` instead of `this`
- `require()` in dependencies

Note that we could get fancier, but I say keep it simple so the diff with the original is small.
Please don't speculate about legal issues.