Fix display of large components
Fix display of large components

Add CSS to allow for oversized components to scroll in all directions. See [issue #1225](https://github.com/storybooks/storybook/issues/1225#issuecomment-307259951).
rhalff/storybook,storybooks/storybook,rhalff/storybook,jribeiro/storybook,jribeiro/storybook,kadirahq/react-storybook,rhalff/storybook,storybooks/storybook,storybooks/storybook,jribeiro/storybook,rhalff/storybook,rhalff/storybook,jribeiro/storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,kadirahq/react-storybook,storybooks/react-storybook,storybooks/react-storybook,rhalff/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook