Add a real family tree view

[mrysav]

The current "family tree" view leaves (ha!) a lot to be desired.

It's not actually a tree at all - just a poor use of responsive layouts.

I don't know how you can do it, and I'm not smart or frontend-savvy enough to know where to start.

Acceptance Criteria

1. Replace the view in views/people/show_family.haml with a real family tree

This can be rendered server-side or client-side, in Ruby or in Javascript.

If you need additional API endpoints added, or any changes to the underlying Ruby controller code, that's totally cool, but please make sure to discuss the changes first and add a test for it.

At a minimum, this tree should display (as a tree):

1. The target person (ie. the person whose page you're on)
2. Their parents
3. Their parents' parents (ie. their grandparents)
4. Links to each person displayed

Displaying the target person's siblings and children is highly desirable, but not required.