Use double-colon syntax for pseudo-elements

The fact that IE8 only recognizes :before and :after with a single colon is mentioned in the notes already.

http://www.w3.org/TR/css3-content/#pseudo-elements: “Authors are encouraged to use the new two-colon forms.”
Update web notifications

Opera 25 will support web notifications. Sources: http://blogs.opera.com/desktop/2014/08/opera-developer-25-supports-web-notifications/ and http://dev.opera.com/blog/web-notifications-in-opera-developer-24/
Update to match usage of SwiftShader

Chrome only uses SwiftShader on Windows and Opera doesn't use
SwiftShader anywhere.
added attr feature
data update
Merge pull request #692 from GeertDD/patch-1

Use double-colon syntax for pseudo-elements
Merge pull request #701 from Ugoku/patch-2

Update web notifications
Merge pull request #702 from gutkowski/master

Add CSS attr() feature
minor tweaks to new CSS attr file
Remove Safari 6.1 from Page Visibility API

The Visiblity API does NOT exist on Safari 6.1, it is first introduced in Safari 7. This should be corrected
Update link
Update ambient-light.json

Link updated
Added support for the Screen Orientation API
data update
Merge pull request #684 from jrmuizel/master

Update to match usage of SwiftShader
Merge pull request #706 from craigbarnes/patch-2

Update link
Merge pull request #707 from AurelioDeRosa/patch-1

Update ambient-light.json
Merge pull request #703 from xlexi/patch-1

Remove Safari 6.1 from Page Visibility API
Update screen-orientation.json

It's Opera 25 that will start the support
data update