Inject events via [[UIApplication sharedApplication] _enqueueHIDEvent:]

Digging into EarlGrey again and all the technical crazy/beauty that's in there. This is such an awesome project.

So. Did some research around the use of `IOHIDEvent` since both KIF and EarlGrey need to use that, and found out that WebKit's TestRunner is doing that as well - but slightly differently than the approach on our testing tools here.

Check out this line specifically:
https://github.com/WebKit/webkit/blob/master/Tools/WebKitTestRunner/ios/HIDEventGenerator.mm#L265

The whole code and handling is interesting and while I don't know what the difference yet, is, see this issue as a TODO to investigate more. Can't promise I'll find the time but maybe one of you wants to take a look if this might be useful.