Better error handling?

`react-transform-catch-errors` only applies to user code - not modules.

This means that when making errors inside a devcard while developing them, errors leak out.

I'm not sure yet whether this is only really a problem because it's in dev.

The component tree looks a bit like this:
- Devcards
- DevcardNamespace
- Devcard
- Actual card body
- Component being developed

But error transforms are only applied at the bottom.

I think it might be preferrable to redbox individual cards. Rather than using https://github.com/KeywordBrain/redbox-react - which takes over the whole page, I think we should only redbox up to the card boundary.