CSS Classname Fixes

Fixes an issue where parsing would fail with the error `XPath error : Invalid expression` if only a classname was used. For example, it would fail when using `.date` instead of, say, `div.date`. Also fixed an issue where, no matter what element you called `-CSS:` or `-enumerateElementsWithCSS:block:` on, it would always execute that CSS in the context of the entire document, not just that specific element.