Bump version to 1.9.1

diff --git a/Makefile b/Makefile
index 618b518..2d9f86b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 VERSION = 1
 PATCHLEVEL = 9
-SUBLEVEL = 0
+SUBLEVEL = 1
 EXTRAVERSION =
 NAME = Unnamed