0.4.0: Render passed-in components. (#17)

You can now also pass in a component to be rendered instead of an already-rendered React element. If you pass in a component, it's passed closeThisTest function as a prop, so you can use this to close component tests that open modals (see #14).

There is a little extra room at the bottom of the component tests screen so that the last component in the list won't get covered by the 'Close' button.