`.jsx` linting is now in-scope for the `npm run lint` command, and
I linted the base files and some of the viz, there's still quite a bit
of work there, but that's a first pass on it.
* Allowing for templated urls in iFrame
This can allow for passing {{ width }} and {{ height }} as dynamic
attributes in the iFrame's URL.
The new method Slice.render_template method could do more eventually
exposing more variables to be used in dynamic strings.
* Passing function references
* js linting
