Use the detected vendor prefix for transform and transition css

The carousel wasn't working for me on safari with jquery 2.1.1 because safari doesn't support `transform` (just `-webkit-transform`) and jquery's css method doesn't set vendor prefixes as far as I could tell. This problem manifests itself when you try to drag the carousel with an error like:

```
owl.carousel.js:705: undefined is not an object: 'this.$stage.css("transform").replace'
```