Add the clean role to our make file

Makefile

@@ -5,9 +5,13 @@ TARGET=$(PACKAGE)-$(VERSION)
 all:
 	$(info Available options)
 	$(info  - package: Builds a tar package ready to be uploaded to marmalade)
+	$(info  - clean: Clean the build directory)
 
 package:
 	mkdir -p $(TARGET)
 	cp hackernews.el hackernews-pkg.el README.md Screenshot.png COPYING $(TARGET)
 	tar cf $(TARGET).tar $(TARGET)
 	rm -rf $(TARGET)
+
+clean:
+	rm -rf $(PACKAGE)-*.tar