Add tests for HTMLBars attribute hook/helper.

Add tests to confirm we are using `setAttribute` for some level of escaping (equivalent to what we have today with `{{bind-attr}}`).

Also, updated to ensure that rerenders happen in the `render` queue.
> lookup-helper file?!

@mixonic  - Don't you start with me mister, remember I was the one to move this into a specific helper file...

Seriously, though, move to `hooks/` or `helper/` I don't like it here.....