Kunal/touching hidden sprite

Addresses #233, #472. 

If the asker's block is hidden, still returns true if touching.
If the surrounding block is hidden, returns false.
Ah, I didn't see Brian's comment, but 2 is inconsistent with scratch. (At least, it is in my testing). 

For 1, you're probably right, I've seen both in _Snap!_ so i'm not always sure if one is more correct or not...