Drop cssUrl parameter to NgComponent since .css is empty (Chap. 6-7)

The component folder holds the files for the two components
search_recipe and view_recipe. Given that one of these has an empty
.css file, it seems reasonable to drop it, reducing the clutter and
driving home the fact that the `cssUrl` parameter is optional.
Merge pull request #52 from chalin/patch-6-drop-empty-component-css

Drop cssUrl parameter to NgComponent since .css is empty (Chap. 6-7)