Schema.org span nesting improvements

So, it turns out that the <a href> was causing a new "chain" to be
invoked, thus nesting the <span> elements for properties within the <a
href> actually caused the properties to be attached to that new chain
rather than the containing object. Therefore, wrap the <span> elements
around the <a href> elements where applicable.

Thanks to Manu Sporny in #rdfa for helping me to sort this out.

Signed-off-by: Dan Scott <dan@coffeecode.net>