Show a finer-grained table of contents in sidebar

According to the sphinx docs we should be able to do something like:

```
html_sidebars = { '**':
['localtoc.html',
'relations.html',
'searchbox.html'
]
}
```

in `conf.py`, unfortunately for whatever reason this makes the landing page for the book (and every page actually) a blank white screen on chrome and firefox :shrug:

This ticket is done when:
- We have a fine grained table of contents in the sidebar
- It actually works without nuking all content in the book.

I suspect this is a css issue because the page source still contains the content of each `.rst` file. I bet the sidebar is expanding to the whole screen or something strange like that.