Bug 894246: Update webfont CSS
 - Cache-bust Open Sans fonts
 - drop SVN include
 - drop extra .eot
These changes are based on http://www.fontspring.com/blog/the-new-bulletproof-font-face-syntax
Merge pull request #1184 from sgarrity/bug-894246-font-cache

Bug 894246: Cache-bust Open Sans fonts for IE