Ignore element names that aren't found in the list of known selectors. This speeds up cascade calculation tremendously.
rename method to something more sensible
Merge pull request #554 from amro/cascade_optimization_issue

Cascade optimization issue
Lower mem and faster CSS cascading. Fixes #555 and #553. New test took 16.85s before and 0.033s after.
Merge pull request #559 from amro/css_memory_perf_fix

Lower mem and faster CSS cascading. Fixes #555 and #553.
Fix font-size inheritance and cascade both being applied, which caused font-sizes to be doubled in some cases
Merge pull request #560 from amro/fix_incorrect_fontsize_inheritance

Fix font-size inheritance and cascade both being applied,
Merge branch 'develop' into classattachments