peek(1): better error on piping

src/peek.c

@@ -88,7 +88,8 @@ int main(int argc, char *argv[]){
 		if (!allow_nonterminals && isatty(STDIN_FILENO) != 1) {
 			(void)fprintf(
 			    stderr,
-			    "%s: Must be run in a terminal (option -i skips this check)\n",
+			    "%s: Must be run in a terminal (specify -i to skip this"
+			    " check)\n",
 			    argv[0]
 			);
 			return EX_USAGE;