Allowed undefined getDirectionBordering result
Allowed undefined getDirectionBordering result

Sometimes, the bordering direction should actually be undefined (such as
when one is exactly on top of another).

Fixes #34. Fixes #37. What a great bug fix.

dlingenau/FullScreenPokemon,syo/FullScreenPokemon,gpnoel/FullScreenPokemon,FullScreenShenanigans/FullScreenPokemon,FullScreenShenanigans/FullScreenPokemon,dlingenau/FullScreenPokemon,gpnoel/FullScreenPokemon,gpnoel/FullScreenPokemon,syo/FullScreenPokemon,dlingenau/FullScreenPokemon