Print usage to stderr when cmdline errors occur

vaporget

@@ -110,7 +110,7 @@ while getopts pdm:h f; do
 			echo "${HELP_TEXT}" && exit 0
 		;;
 		\?)
-			echo "${USAGE}" && exit 1
+			echo "${USAGE}" >&2 && exit 1
 		;;
 	esac
 done