Correctly validate map colors. Fixes BUKKIT-4984

The validation check in CraftMapView.render(CraftPlayer) filters out any
values less than 0. As of Minecraft 1.7, -128 through -113 are valid colors,
so filtering them out prevents some of the new colors from being sent.

This commit fixes the issue by adjusting the validation check to include
any values less than or equal to -113.  As the minimum value for a byte is
-128, no invalid colors are included.