Animation stops when moving diagonally

[continentaldivide]

Implemented diagonal movement before getting sprites working. Didn't realize I was creating a problem for myself since the sprites don't have diagonal animations.

Seems like there there two possible fixes for this:

1. Limit player movement to cardinals. I'm leaning against this one -- diagonal movement feels a little bit better and I think the game would feel a little janky without it.
2. Allow either animation to play when moving in two directions simultaneously. HandleMovement() is going to need to be re-engineered a bit for this to work as I wrote it from a place of assuming the character moving one direction meant no other directional input was happening. This is probably the better solution albeit a bit more work.