Added warning for outdated servers.

For those vulnerable to piston grief due to the addition of slime
blocks, which the Spigot team did not address in early versions of 1.8.

src/me/ryanhamshire/GriefPrevention/BlockEventHandler.java

@@ -474,6 +474,8 @@ public class BlockEventHandler implements Listener
 		//pulling up is always safe
 		if(event.getDirection() == BlockFace.UP) return;
 		
+		try
+		{
     		//don't track in worlds where claims are not enabled
             if(!GriefPrevention.instance.claimsEnabledForWorld(event.getBlock().getWorld())) return;
     		
@@ -524,6 +526,11 @@ public class BlockEventHandler implements Listener
         		}
     		}
 		}
+		catch(NoSuchMethodError exception)
+		{
+		    GriefPrevention.AddLogEntry("Your server is running an outdated version of 1.8 which has a griefing vulnerability.  Update your server (reruns buildtools.jar to get an updated server JAR file) to ensure playres can't steal claimed blocks using pistons.");
+		}
+	}
 	
 	//blocks are ignited ONLY by flint and steel (not by being near lava, open flames, etc), unless configured otherwise
 	@EventHandler(priority = EventPriority.LOWEST)