Fix skipped collisions between tiles about phaser-arcade-slopes HOT 3 CLOSED

Try adding heuristics for the square tiles too, as absurd as it might seem.

You'll probably need to allow returning the preferred separation axis from heuristics callbacks, to handle each edge case (literal edges... in this case... oh).

from phaser-arcade-slopes.

This is fixed for square tiles.

Let's see what we can do about slope seams next. Again, it only seems (hah) to affect bodies that are particularly small relative to the tile.

from phaser-arcade-slopes.

Covered most cases, but edge cases include entering and exiting square tiles at diagonals. This isn't really the right solution, but it helps. We can wait for 0.3.0 for the real fix.

This will do for now.

from phaser-arcade-slopes.