click-and-drag action in the game of life animation is offset from where the user clicked

[lucas-28]

I realize this is not a pressing issue at all but here it is:

When you click once on the Signup Page banner, the color explosion happens right where the mouse click occurred, while when you click and drag, the color appears offset about 40px below the mouse.

[MoralCode]

this might be related to PR #42.

[MoralCode]

upon a further inspection this appears to be as simple as not taking the offsetY value from handleMouseDown into account when requesting another animation frame in handleMouseMove (here is where it is in code)