Improvements with version 1.2.3

• BUG FIX: Removed dotnetzip-for-unity so we can use SuperTiled2Unity scripts with asmdef files
• BUG FIX: Protect against GZip and zlib libraries throwing exceptions on some platforms (found on the odd Linux build of Unity)
• BUG FIX: Fixed crash with tile animations on tilesets that have had tiles removed from their collection