Adds a builtin flip animation

I've added a horizontal and vertical flip animation to transition from one view another. Both views need to be positioned on top of each other.

```
var animation = require('alloy/animation');

animation.flip(fromView, toView, animation.HORIZONTAL, 750, finishCallback);
animation.flip(fromView, toView, animation.VERTICAL, 750, finishCallback);

animation.flipHorizontal(fromView, toView, 750, finishCallback);
animation.flipVertical(fromView, toView, 750, finishCallback);
```

JIRA: https://jira.appcelerator.org/browse/TC-2750