Add additional hooks for callers:

* Resolve relative URLs.
* Set priority on any stylesheet implementation.
* Substitute content during XML Conduit traversal in place of computed styles.

Update Stylish HTML Conduit to use fixed psuedoelement handling.

Rework psuedoelement infrastructure so they can be their own boxes.

Add support for psuedoelements/classes.

Improve code cleanliness to avoid future bugs.

Add method to override CSS inheritance.

Parse HTML 'style' attributes.

Fix parser freezes, blocking issue for Rhapsode.

Ignore invalid selectors.

Aid attribute sorting, fix install of internal modules.

Fix cabal file.

Switch to new namespace for consistency with other modules like css-syntax.

Index style rules to quickly narrow down which ones match a given element.

Add and pass some unit tests.

Implement basic parser. TODO test.

Model the tree being matched, to be converted from XML conduit.

Init module.