Add itemscope to make itemprops legal

Three of the HTML5 files demonstrating the `withinText` markup were illegal HTML5 (according to http://validator.w3.org/nu/). This is because they were using `itemProp`, but were not inside of an item (didn't have an ancestor with `itemScope` set). The item seemed to be the entire body, so I added `itemScope` to the bodies of the files with problems, and now they validate. An alternative fix would be to remove the `itemProp` attributes, since they aren't referenced in any way by the global rules.
Sorry about the other changed lines- my editor removed trailing whitespace.