A couple of fixes, and a new animationPoint property for the HUD

Great library! What do you think about merging in these changes?

I added a new `animationPoint` property for the HUD that allows `show:` and `hide:` to consistently animate from/to a specific point. This can improve the `show:` animation which currently always animates from the top left corner. `hide:`, on the other hand, always hides into the center. The new property gives you a way to pick a specific focal point.

I also made a couple of fixes based on some clang analyzer warnings, and improved rendering of the HUD to avoid some non-integral positioning.