old_contents: /* @flow */
  import { Route, Switch } from 'react-router'
  
  import CreatorContainer from 'containers/CreatorContainer'
  
  type RouteDefinition = {
    component: ReactClass<*>,
    key: string,
    path: string,
    exact?: boolean,
  }
  
  const defs: Array<RouteDefinition> = [
    {
      component: CreatorContainer,
      key: 'document#edit',
      path: '/',
      exact: true,
    },
  ]
  
  export default (
    <Switch>
      { defs.map(props => (<Route {...props} />)) }
    </Switch>
  )
  
new_contents: /* @flow */
  import { Route, Switch } from 'react-router'
  
  import CreatorContainer from 'containers/CreatorContainer'
  import PreviewContainer from 'containers/PreviewContainer'
  
  type RouteDefinition = {
    component: ReactClass<*>,
    key: string,
    path: string,
    exact?: boolean,
  }
  
  const defs: Array<RouteDefinition> = [
    {
      component: CreatorContainer,
      key: 'document#edit',
      path: '/',
      exact: true,
    },
    {
      component: PreviewContainer,
      key: 'document#show',
      path: '/preview',
    },
  ]
  
  export default (
    <Switch>
      { defs.map(props => (<Route {...props} />)) }
    </Switch>
  )
  
subject: Add /preview routing