adding the method waitForAnimationsFinishedForTimeInterval: 

to KIFTestActor: It tries to guess if there are any unfinished animations and waits for a certain amount of time (3 seconds for now) to let them finish. This improves the stability of our integration-tests among the different iPad-Generations, where some tests failed on slower devices as they needed slightly longer to finish an animation than other devices, and we constantly had to add waitForTimeInterval:-calls and adapt the timeinterval.

A question in general is, if this functionality should be configurable (through a property? #ifdef?) and if the timeout should be configurable (three seconds works fine for us and seems reasonable).
In [other parts of KIF](https://github.com/kif-framework/KIF/blob/master/Additions/UIView-KIFAdditions.m#L618-620), there is a check for `*stop` in similar places:

```c
if (stop != NULL) {
    *stop = YES;
}
```

Perhaps this could be added here to maintain consistency?