Use correct render type for turtles

This fixes them not rendering particles when broken. Particle rendering
is a little janky right now, as it uses the whole texture - we should
probably split up the texture into smaller images. Fixes #315

src/main/java/dan200/computercraft/shared/turtle/blocks/BlockTurtle.java

@@ -58,7 +58,7 @@ public class BlockTurtle extends BlockComputerBase
     @Deprecated
     public EnumBlockRenderType getRenderType( IBlockState state )
     {
-        return EnumBlockRenderType.INVISIBLE;
+        return EnumBlockRenderType.ENTITYBLOCK_ANIMATED;
     }
 
     @Override