fixed demo challenge

ps-grammar/demoChallenge/commands.jsgf

@@ -2,10 +2,9 @@
 grammar bebot_demo;
 public <statement> = [tobi] [please] <command> [please] [tobi];
 
-<command> = <clean> | <party> | <teach> | <mapping>;
-<clean> = clean up | start cleaning;
-<mapping> = start mapping;
-<party> = [the] party starts | party beginning;
+<command> =  <mapping> | <clean> | <party> | <teach>;
+<clean> = (clean up) | (start cleaning);
+<mapping> = ( start mapping );
+<party> = ( [the] party starts) | (party beginning);
 <teach> = ( (this is [a | an | the] ) | ( these are [the] ) ) <object>;
-<object> = [other] ( trashbin  );
-
+<object> = trashbin;