Fixed "unknown command" on vanilla commands with no args (even though it's intended behavior...)

src/main/java/org/bukkit/command/defaults/GameModeCommand.java

@@ -54,6 +54,6 @@ public class GameModeCommand extends VanillaCommand {
 
     @Override
     public boolean matches(String input) {
-        return input.startsWith("gamemode ");
+        return input.startsWith("gamemode ") || input.equalsIgnoreCase("gamemode");
     }
 }