Investigate replacing styleguidist with storybook docs

[nathanyoung]

The Docs storybook add on might be a good replacement for styleguidist.

https://github.com/storybookjs/storybook

We use storybook anyway, so it might be simplier to combine it with documentation and also use knobs to show variants.

[osbornm]

Understand what stories are for documentation and what stories are for development.

[eddiemonge]

Support additional documentation that isn't components like hooks, media queries and other things