Make help command use descriptions and usages

src/main/java/wtf/beatrice/hidekobot/commands/message/UrbanDictionaryCommand.java

@@ -36,6 +36,18 @@ public class UrbanDictionaryCommand implements MessageCommand
         return false;
     }
 
+    @NotNull
+    @Override
+    public String getDescription() {
+        return "Look something up in the Urban Dictionary.";
+    }
+
+    @Nullable
+    @Override
+    public String getUsage() {
+        return "<query>";
+    }
+
     @NotNull
     @Override
     public CommandCategory getCategory() {