Use fully qualified class names to avoid conflicting on Query from within the Filter namespace

I made the change to HasParent and then discovered that someone had already fixed this bug in the HasChild class.

Personally I think using fully qualified class names is nicer / cleaner, so did that and brought the HasChild class into line, but not really fussed either way – if you'd prefer aliasing just say.

Is there any documentation on how to run the tests locally? I've had a quick look but can't see anything, so going to let Travis run them for this change…

Thanks.