Files without JSX are not transpiled by babel

Repro:

Add a new file that doesn't use JSX:
```
import styled from 'styled-components'
```

export const SomeComponent = styled.divfont-size: 24px;;


2. Try to load the docs page. 
3. Fails with `Uncaught SyntaxError: Unexpected token import`
4. Add in some JSX to the file and it works fine.

This is probably due to dynamically building the page with hot reloading and tricky webpack context stuff (see `/docs/Root.js`). This would be the first time this was caught because all other components that are shown have JSX in them. 

Current workaround is to include JSX in the file.

weaveworks / ui-components

Files without JSX are not transpiled by babel #38