Implement SVG stylesheets

Includes a lot of testing improvements but most prominently support for SVG stylesheets. These have some specialties, like camel-case DOM elements. Also, I fixed previously not run tests (such as color / grid).  Please check the individual commits for details. Lastly, I bumped the version to 0.9i (and added a tag but I don't see it in the pull request). Once you accept this, could you please push a new version to PyPI? Thanks a bunch!