update CSS Filters implementation status

- [Support will be enabled by default in Firefox 35](https://hg.mozilla.org/mozilla-central/rev/697c4b245de0)
- add corresponding [Chromestatus.com entry](https://www.chromestatus.com/features/5822463824887808)
Merge pull request #756 from myakura/update-cssfilters

update CSS Filters implementation status