Add hook for callers to run their own tests against attributes.

Evaluate attribute namespace selectors.

Parse namespace selectors.

Improve documentation, release version 1.2

Rework psuedoelement infrastructure so they can be their own boxes.

Add support for psuedoelements/classes.

Improve code cleanliness to avoid future bugs.

Data.CSS.Style.Selector.Index: fix potential crash.

Draft alternate API.