Activate admin site

My thought was that production would be the only place we *would* want this enabled. So if that's the case, we should not use it. At least with defaults, it doesn't look like a method that our team would use to browse models, when the source is available to us.

I think it makes sense if we take this all the way and put documentation into our `models.py` files that will be useful to our client.

I'm going to pull this out in a separate commit to be squashed and we can see what other team members think of this.