Fixed isSupported not returning true for Safari

This call:

```javascript
var supported = $.keyframe.isSupported();
````

will now evaluate to **true** for Safari (Tested on Version 7.0.1 (9537.73.11)).

Please note, we have to "re-minify" to the .min.js file to reflect these changes.

Signed-off-by: Arné Schreuder <arne@consulta.co.za>